An obvious disadvantage of not having deadtalk on is that when someone talks to you after they get shot you can't see what they say, this can also be an advantage since most of the whinning takes place by the "dead". Most of the time what people say isn't worth reading... but it's confusing when you come into the conversation midway... not a big deal usually. Then there's the advantage the rodger wilco etc users would have, as previously mentioned. If duplicating or creating a similiar built-in voice system is out of the question maybe making it easier to use the existing programs somehow might be a good thing. A locked team chasecam would be fine with most people I'm sure.
Personnally I don't care if "dead" people can talk to their alive teammates. I tend to recon more than most only in hopes others will do it for me.
The jails can be made so only one team spawns in them, for example the map routes (a great map btw) has 2 jails, one for each team, and people in jail can shoot out into the live area. If you want to turn pball jails into more of a jump game then make 2 jails. (or 4 or whatever)
Basically, I like deadtalk on, deadteamtalk can go either way. If people use deadtalk for recon then all will see it and hopefully play accordingly.