Haven't we tried an all-teamtalk day in the past? I don't remember it working out too well.
I wouldn't mind having the teamtalk-only option available, but I'd rather leave it to the voting mechanics that the other options (nocrits, etc) are subjected to than have it come up at the beginning of every single map.
Speaking of those voting mechanics, the percentages across the board to get those to pass should be lowered a bit, I think.