I think TNT SHOULD blow up in Multiplayer, but not delete any blocks. It could send a person flying off into one direction if detonated on them or by them, but not destroy anything. This could make for some fun games.
A. Server.properties has the ability to have ops only spawn it
B. It becomes a command and can be edited who gets it
C. A new group becomes added between Members/players and Operators.
D. A timer on how long you can place TNT (Example: Five or three seconds.)
E. Tnt is rare and only given one pair on start.