2) Crossing the line. There's an element of chasing the horizon in incorporating monster abilities. Every spell a wizard can learn is already in ten thousand spellbooks. Monsters tend to have unique, bizarre, and flavorful abilities that magic can't (or doesn't bother to) replicate. Out of universe this is probably because monsters themselves are supposed to be sundry in most cases, making the writers a little less uptight than when designing player options. The above paragraph was right in that there's a sense of randomness to what you get, but it should be more like there's a sense of discovery. Like I've gone out and found something nobody else has before. Obviously this is all a game and was all written by somebody ahead of time, but the pseudo-randomness of not knowing what I'll find out there does a lot better job of maintaining the illusion than "and then the Wizard bought a scroll from Magic-Mart and scribed it permanently." This part may ruffle feathers, but the fact that some monster abilities CAN be imbalanced is part of the reward; Blue Mages are the only class that by leveling up gain the opportunity to earn an ability through hunting and then combat rather than just gaining new abilities for free. It feels higher demand, but you might get a better or at least stranger reward out of it. The monsters themselves are loot. And if you do know of an ability you really really want, then you can just tell your DM in the same way some people will wishlist a particular item, and it's up to them if they want to find a way to incorporate it.