Add a mineral component.. or a mineral point cost?
Mineral points can be raided.

Doesn't seem to be much of a penalty to being blown to bits.
You really don't gain or lose much regardless of the side of the cannon you are on?
Actually if you add it all up, even attacking is a losing proposition.

This idea might make raiding more worthwhile as well as make people realize how much they spend. Might limit how much they could do it too?

Might be a case of be careful what you wish for...