I think the basic difficulty with this is one cannot necessarily just dial in a level to a creature and expect it will be reasonably balanced.
It's true that bandits and Grimswarm work this way, but they were also designed that way as well, including having their skill sets increase with power with increasing level.
Darkstone is actually one of the older hunting grounds in the game. MTKs are still not on the BCS system. So it's kind of a polar example asking for some of the oldest, weirdest creatures to be ported into the skin of some of the latest creature types. Still, even with a different example I don't think the answer fundamentally changes. (One could even use the reverse logic, which is that MTKs probably need their code updated anyway, so why not go all out?)
All in all, everyone would like more hunting in various areas (capped, undead gap, etc) but while this solution is interesting on paper I think it would never happen in practice. If it was done or seriously considered, the obvious thing (to me) is to just apply the same formulation, from 0 to 100, to all hunting grounds. (If the code was done for DS and done well, in principle it would be portable.) This would certainly have some pretty cool implications: capped Citadel hunting, capped shan hunting, no more undead gap, etc etc etc. But I think this would be a different game at that point. The game as it is, each hunting ground (generally) has its own flavor and level ranges.
You're literally better off asking for a DS expansion that includes capped creatures. Also not likely to happen soon, but more likely to happen ever. (Or, pick your specific hunting ground example.)
