eta> I think 'working' is pushing it. The only game that really seemed to work without major problems (although had no sound) was Pinball Fantasies ;-)
and yes, I agree, the handling of things in the Jag driver is reversed. Considering it's one of Aaron's drivers it's absolutely shocking in places the way it abuses the MAME systems, direct memory accesses, allowing ROM to be overwritten etc., had I not known I'd swear some of it was done by Acho ;-)
If I'm not mistaken, a malformed / invalid / badly handled blit operation right now can erase RAM, ROM, IO, or even completely crash MAME because it's simply getting a direct pointer to whatever region is involved, no matter how wrong the calculation might be.
CoJag should have been build on solid Jaguar foundations, not the other way around. It will need work, but we'll get there eventually ;-)