As have I. The problem is that 1st level wizards (I am aware that they are technically called Magic-Users), might roll crap for their initial 4 spell rolls (5 if your Dm was generous). Compared to the typical 2 first level spells and 3 cantrips of 3.5th edition, your 1st ed 1st level MU is possibly going to get shafted at the start. Granted, after about level 5, the 1st ed wizard starts to get a lot more viable (nearly equaling 3.5 ed), the cavet remains the 1st level.
Back on topic. (I do miss those level titles, nothing like being a prestidigitator, lol, seriously though, back on topic) Do you think that 15-20 xp sounds reasonable? As far as Ainz is concerned, if we use the estimation method, we would get 1200-1600xp. This would be rather large. (The 10,000 xp is the estimate I use for a Star Wars force sensitive with maxed out specialization trees, force powers, and skills [in the career]). If I only consider genesys rules, maybe 10xp per level sounds better?
Obviously Ainz, is a power-fantasy character (that is half the fun of trying to PCify him). Nonetheless, I am still putting this forward as a thought experiment. (The more difficult challenge [if your up for it] is to try and create a conversion into Anima: Beyond Fantasy).
An idea to import epic spellcasting: I was thinking of adding what I dub an Advanced Skill to the game. A special 5th tier talent is required, with GM permission (and with an ingame quest after maxing out the basic version of a skill), that qualifies you to start taking ranks in the advanced skill (note: that it is never [most likely] a career skill). Each rank of the advanced skill gives 1 boost die to every use of the basic version, but also allows what would be considered impossible checks to be made with that skill. Basically, instead of flipping a destiny point to do an impossible task, you would roll against an advanced check (it would have its own version of impossible [god-tier miracles and the like, that require a destiny point flip]).
In keeping with the absolute disorganization and lazy writing with my usual response, I had a question about Super-characteristics. What is the max number (if any) of additional yellow die? This is just an out-of-topic side question. I was thinking it works like the World of Darkness rule set in allowing for potentially infinite rolls, but I can also see the interpretation that seems to suggest a max of 2 additional yellow dice. Which do you think?
Thanks for your response.