Ad-hoc evaluation of unique allies as contract targets:
General consideration: The expectation is that the best targets are those that have low stats, but are highly costed for amazing and recurring abilities.
Lore Anborn: 8 threat cost, fair stats, relevant traits. Recurring traps is a relevant ability. Fair target.
Leadership Anborn: 8 threat costs, fair status, relevant traints. Increase engagement cost and dealing damage ok, but not amazing. Ok target.
Angbor the Fearless: 5 threat cost for a fair quester. Relevant traits. The valor trigger nombos with the low threat cost. Niche target.
Arwen: 5 threat cost, relevant traits and her tried and proven ability make her a good target. To consider: her ally cost of only 2 which is part of what makes her great in the first place. Also you can't use her hero version. Good target.
Azain Silverbeard: 7 threat cost, relevant traits. The ability is interesting, albeit a bit niche. Could be an interesting pick for quests with a number of low HP enemies. Niche target.
Barliman Butterbur: Nope.
Beechbone: The general problems with ents is that it is their ally cost that makes them attractive. Paying for the stats in threat and starting with an exhausted hero is meh.
Beorn: 13 threat costs makes him one of the more expensive hero options out there. His ability is likely a tad better then Tactics Boromir discard ability, but then Beorn lacks his mad readying skills. Niche target.
Bifur: Nothing to see here.
Bilbo Baggins: 4 threat costs for a 2WP quester that does not die to 1 damage. Looks like a good deal. Starting with a pipe is also nice. I expect that he will be a popular target. Good target.
Bill the Pony: The only way to get a hero with the coveted pony trait. Someone will play it for that reason alone, but other than that not very interesting as the main selling point of the ally is that its resource cost is 0.
Spirit Bofur: Nothing to see here.
Tactics Bofur: 7 threat costs for 2WP, 2 ATT and 3 HP is ok. The ability to repeatedly tutor for weapons will surely make him see play. Good target.
Bombur: Maybe against quests with high threat underground locations? Very niche at best.
Boromir: 9 threat cost with two relevant abilities and traits are likely sufficient to make him see play. The contract's readying limitation does matter here. Fair target.
Brok Ironfist: Not very exciting to say the least. You could replace hero Brok by ally brook if the latter bites the dust just for the memes. Meh target.
Ceorl: A hero that can be passed around the table. Very interesting. Fair target.
Damrod: Discard for small benefit. Not very interesting. Meh.
Denethor: Pay for stats with only downside abilities? Pass.
Derwine: 7 threat costs for 3DEF 3P sentinel with built in shadow cancelling? I expect that this will see play. Good target.
Derufin: Discard for small benefits? I do not see the point. Meh.
Dori: His ability to take damage instead of a hero does not shine here. Pass.
Dwalin: Blank ability. Pass.
Spirit Elfhelm: Hot tech against certain quests. Niche target.
Tactics Elfhelm: Blank ability. Pass.
Elladan and Elrohir: Ok alternative to their hero versions with lower threat cost, lower HP and lower off-stat (the one that is not boosted by the sibling). Interesting to have options against Orc heavy quests. Fair targets.
Elrond: 11 threat cost for an additional card at the start of the game and a body does that does not stick around? Pass.
Emery: Blank ability: Pass.
Eomund: Even though his ability requires to discard him, the effect of readying everyone Rohan can be powerful. Niche target.
Eothain: 8 threat costs puts him in actual hero territory. His ability is ok, but not spectacular. Also Imrahil exists. Niche target.
Erestor: 6 threat costs for an interesting ability that is not quite as extreme as that on his hero counterpart. Good target.
Leadership Faramir: This was featured in the article, so it better be ok. I think it is. Ok target.
Lore Faramir: Surely there has to be a quest or two where his ability matter during setup (depening on the precise rules for setup order). Niche``?
Farmer Maggot: Meh.
Firyal: 9 threat costs for a good quester with an amazing ability. Good target.
Forlong: Everyone's favourite unique outlands ally as another hero? Surely this will be a thing with Hirluin and outlanded Imrahil. Good target.
Gaffer Gamgee: 3 threat cost for a hobbit hero will put a lot three hobbit decks comfortably into secrecy territory. The ability is niche, but relevant. Ok target.
Galadriel: Nope. Another white council member that does not like this contract.
Galdor of the havens: Same stats as his hero version, but a interesting different ability. Will see play. Good target.
Galion: 1 threat cost for a third hero will be good enough to make it into secrecy decks wanting another spirit hero. Ok target.
Gamlin: Ability to recur Rohan allies on a stick may make this good enough. Meh stats for 6 threat costs. Niche target.
Ghan-Buri-Ghan: If you ever wanted a wose hero, here is your chance. For only for threat cost, is ability is quite ok. The discard ability will rarely be used, but it's a nice bonus. Good target.
Gildor: Hero quality stats and cost with an amazing ability. This will enable new decks. Good target.
Gimli: 9 threat cost for an allrounder make him fairly expensive. Relevant ability. Ok target.
Gleowine: 3 threat costs for card draw on a stick make this a Beravor light that will fit in a number of secrecy decks. Good target.
Glordfindel: 11 threat costs with a hero-level ability make this an eligible target. Fair target.
Grimbold: Discard hero to feint? Not great, but you get a 2 WP tactics hero for 6 threat cost. Niche target.
Guthalf: 6 cost sentinel tactics hero. Niche target.
Gwaihir: If you always wanted a Gwaihir hero, but the actual hero Gwaihir is too expensive for you, then this will do. The response will fizzle though. Too bad. Meh.
Halbarad: Too high cost for an all-rounder hero. Ability not relevant enough. Meh.
Haldir of Lorien: Also too high cost for all-rounder. Ranged and sentinel are nice though. Niche taret.
Halfast Gamgee: 5 threat cost leadership hobbit hero that quests for 2 and comes with a free resources. This will go in a number of hobbit secrecy decks. Good target.
Hama: Meh stats and discard to use ability. Very very niche at best.
Henamarth Riversong: Everyone's favourite scrier now collects 1 lore resources for round for 3 threat cost. Squishy, but good. Good target.
Ingold: 5 cost for a strong leadership quester. Why not? Fair target.
Ioreth: Covered in article. Good target.
Jubayr: Defender that discards shadow cards. Good target.
Landroval: The question here is whether he can bring himself back. Need some rulings, but likely niche.
Leaflock: An ent. Niche.
Leogolas: Nice to have options. Good stats, traits and ability. Good target.
Lindir: Not sure on the rule here. If his ability triggers before you draw the starting hand, then this may be fantastic, but that I doubt that this is the case. Meh otherwise.
Mablung: A 5 threat cost hero that quests for 2 in ok. The ability to increase an enemies engagement cost (if the setup timing allows it to trigger) is very narrow in application. Niche target.
Meneldor: Another mediocre way to get an eagle hero. Niche for that thematic reason, but meh otherwise.
Merry: 4 threat costs for a 2WP quester that doesn't die to a single damage. If you can afford 3 threat cost more for Sam, then this will be the better option unless you already run him. Niche target.
Nori: 6 threat for an ok ability in a dwarven mining deck. Ok target.
Orophin: 6 threat for a good quester/attacher stat distribution with ranged. Ok target.
Pippin: 4 threat for 2WP and 2HP is ok. Both abilities are very relevant, makeing him a stand-out amongst hobbit targets. Good target.
Prince Imrahil: Nombo time!
Quickbeam: An ent. The main selling point as an ally is his ridiculously low cost. Less good as a hero, though the readying make this playable in some cases I suspect - even with the contract limitation on readying. Niche target.
Robin Smallburrow: 5 threat cost for a 2 quester and an ability that is only occasionally useful at best. Ok, but there are likely better options. Ok target.
Rosie: Everyone's favourite female leadership hero. Good target.
Rumil: Ok stats and ranged, but nothing more. Meh.
Sam Gamgee: I think the hero version is the better one here. However, this may find a spot in a hobbit deck that is looking for another spirit hobbit that isn't Pippin.
Skinbark: Does nothing the first round, but the ability may be good enough in some quests. Haven't checked. Niche.
Sulien: 3 WP for 7 threat cost is ok, but in spirit you could pay 1 or 2 threat more to get Lothiriel or Eowyn. Niche target.
Wigalf: I suppose the readying ability makes him ok, but not exciting. Ok target.
Yazan: Hero grade stats and hero grade ability (albeit on the weaker side). Probably the worst of the Harad allies as targets. Ok target.
In my count that makes 17 good targets and a lot of other options to play around with. Also nothing seemed OP. A very interesting contract overall, that opens up a wealth of deckbuilding options. Happy to see this contract!