So theres no way to get the minis from FFG or so? It seems to me like a huge waste of produced content. I hopa FFG will make a boxed version including minis for the conversion kit.
You could contact FFG and ask, but they don't generally sell bits piecemeal. There is certainly no method I currently know of to buy the minis without simply buying old 1E boxes, where you can find them. There used to be an online store selling Descent for bits, but I believe he ran out of stock (at least of the minis) and hasn't restocked due to the expense involved these days. (He was just buying boxes and opening them.)
I think the conversion kit was mainly intended to be a shout out to anyone who already owned first edition. FFG is generally pretty good about considering their existing fanbase when making new related products. If it motivated people who didn't already own 1E to buy up the remaining stock, that was just cake for FFG.
You don't really need the CK to play Descent. The 2E core box has enough options to keep things lively for now, and future expansions will extend your collection. If you're willing to work with proxies (you can even sub in ettins for giants and such if you want) then the CK gives you MORE, but it's not like you NEED it for anything.
Im even considering getting the first ed box just for the minis, but even that wouldnt give all of them since I would also need all their expansions. How about "booster packs" with a few of the old minis including cards? Nothing like that? Would it be possible to get the first ed box somewhere then?
You can look around on eBay and the like. Descent 1E boxes seem to be pretty expensive on the second-hand market though. This would be why so many people around here recommend proxy figs - it's not hard to find suitable replacements for most of the monsters and it's a helluva lot cheaper.
If you still want to press on with that idea, though, be aware that you really don't need Road to Legend or Sea of Blood at all. Nothing from those two boxes appears in the CK (unless you want to count Nara the Fang in limited edition SoB boxes, but I'm reasonably confident FFG will continue to ***** out the promo figs in future events anyway.)