1) No you don't need 2 servers. The dead people have 30 lives and run around in a separate area of the map shooting each other.
That would mean you have to take every single map out there, add a seperate area to them (favorably at the same location so you have a hint where to put spawnpoints to) not to talk about the increase in map size for all maps. Two servers would solve the problem of adding stuff to all maps though it would cause many other problems (forced switch to another server, regular polling between servers and much more).
About the second suggestion of controlled respawns (I assume we are talking about EAS missions with several mission goals), if the only goal is to create small groups, you can seperate a mission into rounds. Each round is played with one life, after a team is dead a new round will be started. If any objectives had been completed it is completed in the next round too.
The advantage over any respawn based approach is that you dont put any human player in an environment he has more knowledge of than he should have and you would still have groups spawning together.
For the free ghosting part. IMO if you don't allow free ghosting you somehow have to make sure that players don't get bored either by UN17's seperate map area or anything else. I would prefer something more simple between rounds like a good game of pong or tetris
