There's actually already a mode that is in the same spirit as survival mode in MW3. That would be Firefight. Also, no. Having multiplayer bots could be something for custom games. Being able to add bots when you don't have enough players would give those without an XBL connection or Gold account the opportunity to play regular gametypes with other opponents. Instead of having to gather a whole bunch of friends, they could simply add bots to the game to play with. I fail to see how this would ruin the game in any way. Besides, there's nothing wrong with the survival modes in those two games you mentioned. They're both fun for what they are, and offer something different from the regular matchmaking experience. Firefight in Halo: Reach and MW3's survival mode offer the same thing. They allow players the chance to go up against AI opponents in different waves until you either win or die, though I'm not sure if you can actually win in MW3's survival mode or not.
Having a mode or feature that is like something in Call of Duty does not automatically make it a bad thing. I see this kind of attitude far too often. Something in one game resembles something found in Call of Duty, so that means it's bad. I'm not necessarily saying that's the attitude you hold, just that I see that kind of attitude far too much.