So since Rook can switch places with your markers you can actually use him offensively. Take two proximity mines and then he can switch places with the mine to have the mine explode on the unit that you want it to explode on.

I don't know that that would work. It would let you reposition mines, for sure. But the mine it's self says a unit has to move within 3" of it. This could be taken one of two ways. Those being a unit has to move from outside of to inside of 3" of it. The other being that there has to be movement in it's 3" radius. It's not an AOE, so it doesn't have the same rules (EG beginning an activation in an AOE triggers it).

I'm going to post this over on in the rules section and see what people think/get an official response to it. It really does seem like it could go either way, especially since the situation of something managing to be within 3" of it without having moved there is really uncommon.