P4s and Proximity Mines

[Spikedude]

You could just keep a count of how many active explosives a player currently has. Each thing could get a different value too. Like maybe you can have a total explosive power of "10" active at one time, and each p4 takes up "4" of that, but each tripmine only takes up "2." Once you've placed over your "10" (ie two p4s and a tripmine), each subsequent bomb-lay will cause your oldest active bomb to explode.

We could even make another level system type thing with this. After you get x number of kills with explosives, you can have 1 more active bomb.

Poeple would still be able to place proximities on top of P4s, but they'd either have to team up to get all the entrances or they would have to guess which entrance you'll use.