Dont feel the need to get defensive, as these questions are purely curiosity based: Why do you want to be able to disable the special enemy types? Do you not like them thematically, or are you a relatively new player and thus find them difficult to deal with?
Cataclysm can be a fairly brutal game for new players, im fairly new myself. But the reason i ask is because i find the combat in cataclysm is a little on the dull side at times. There are two main tactics that seem viable. Either you kite enemies with a ranged weapon, or you lure them onto tiles which are hard for them to climb onto, and then proceed to attack them and get plenty of free hits in. If one were to start removing the special variety of enemies, the game ceases to have much challenge or strategy and begins to feel somewhat stale because you end up approaching all of the battles the same way… you go hide in a house and fight them as they crawl in the windows, or use bushes and trees while in the wild.
While i think that having the option to disable these things can be a good thing, it does have a few drawbacks too: Its going to be even harder to balance if players are playing with different sets of enemies enabled. Also many items in the game could become unnecessary or useless because the threats that they were created to deal with had become disabled. But with that said, it would allow people to play the game their way, on a difficulty level that they found enjoyable.
Like theShaikan says, there is a build of the game out there that simplifies the monster types somewhat, ive not played it myself however. You can find the thread for it here: http://www.cataclysmdda.com/smf/index.php?topic=159.0
