Disabling invincibility via the "Set Invincibility" trigger does not appear to work for Khaydarin crystal formations. I'd assume it's because the "Invincible" flag in units.dat is raised. Is there a way to make this work via EUDs? Has anyone researched it and will that particular offset work on SC:R?

Yes, "EUD: Modify Memory"; Modify memory at Death Table + 223220, Set to 1. You must disable invincibility via "Set Invincibility" for all Khaydarin Crystal Formations that have been placed before the EUD trigger was run.