Yep, Mattn doesn't want it, therefore it's not going in. It's not up for a vote. We work together with give and take based on our areas of expertise, not some kind of free-for-all that would screw up any decision-making process beyond words.
In my view, destructible terrain isn't particularly necessary in a game like UFO:AI -- but I do like the idea of hard and soft cover, having certain surfaces allow bullets or blasts through in a limited way, mediating their damage and/or flight path. It'd be nice to figure out the viability of that idea.
Regards,
Winter