It's funny because I was just thinking about the compressed and unstable crystals from FU. I don't know how much I agree with the stat blocks presented so far (some of them seem too powerful) but I like the idea of them being included.
This being a pretty important part of the EU (which of course is rapidly disappearing) I hope it at least gets a mention in the book.
@scalding: I like you're generic crystal, but I think it may still have too many mods on it. Possibly leave off one of the damage mods. But that's just me. Ilum crystals were the gold standard for a reason, and that still places this within the realm of being viable. But that's just one man's opinion.