It's possible and not hard at all to put in.. the problem is that making a map is more than just throwing some fun stuff in and it will work... objective modes are extremely hard to make good, and the objects are just a minor part of it, you need to build the terrain and synchronize all other statics so the map plays good over-all.. basically take in the "objective" stuff in-to the entire leveldesign.. with objective maps you want to assign importance to a few objects, yet you dont want the entire server to clog up around them (like all 64 players fighting in one place) but at the same time you don't want the objectives to become irrelevant, turning the map into a half-good conquest and a half-good objective map... so its a hard balance..
Blowing up stuff is fun for one guy in about ~3 seconds.. a map needs to provide fun for 64 players the entire round.
A mix of push-conquest and objective/conquest is nice, (spread the action out, but give it "story") and I'm looking into that at the moment.