You can already blow open UFO's with a blaster launcher... This way you can keep the alloys ^^
I think high explosives also work... ^^
Not in the original game (except with XCOMUTIL). Not sure about Open X-Com, but it shouldn't be possible.
I think it should... ^^
I have my doubts - these hulls take multiple hits from nuclear warheads and remain operational. With Elerium explosives like Blaster Bombs, sure; or perhaps small nuclear charges (or equivalents).
like plasma torches...