1. Mine layer or mine sweeper? I don't think the former would be terribly useful, but I'd appreciate the later.

2. I agree it's... annoying... how much the game discourages building up new tanks.

3. They need to do what pretty much every other game similar to this I've seen does, make the "PvP" (in this case, PoC) use a different resource than the PvE content. Maybe crystal tiles that give portal fragments or something you use to run portal levels.