RIFTS as a game is what I would term very crunchy in its mechanics.
What it has going for it, is a very well defined world. It is gritty, scary, and intense. It introduced one of the few systems that tackled super weapons and machines.
Would Palladium RIFTS work as a Play By Post game? Maybe. I would say for storytelling purposes, you have a good time. For the dicing mechanic, you have a guaranteed nightmare. I would say more, but a newer version of the game is being made available and I believe it deserves its own spotlight/thread.