I use a Yamaha Freeride jacket with zip-off sleeves, although I've never taken them off. I don't think it's safe. That particular jacket has several vents and is very comfortable in warm weather.
I just squid it!:squid: Usually just a long sleeve shirt. Stupid I know. :spank: Unfortunately I have had other things to spend my $200 on but hopefully I'll be getting a warm weather jacket soon! Seems like a vest would be about as beneficial as what I wear now so I cant see buying one.
Though the sleeves zip off, I don't think I'd ever take 'em off. I've put a bike down at low speed and caught myself on my elbow wearing just a long sleeved shirt. I had a knot the size of my knee for weeks. The jacket is nice and has a removable liner. All but the back Army logo is easily removed. Granted, I'm proud to be in the Army, but I'm no recruiter.