Get leather for riding comfort. Rain ain't going to hurt it if you keep plenty of conditioner/protector on it. The rain should just bead up and roll off if you do.
Besides, I'm pretty sure Vinyls are endangered.
Yes. Especially the Nauga's used for the Naugahyde.
No bag. I used to have a fork bag but hated it. I'm considering a swing arm bag but probably not until after the new seat. Or maybe I'll do the bag first. I dunno. I'm as indecisive as my wife at the moment.