I don't think he was directly involved in development, just happened to be producer because he was the head of AM2. But he did greenlit the project, furthermore, both the head of SEGA's consumer division and arcade division were guys who worked under him. If nothing else, he helped nurture key talents for the company, his legacy is a lot more than just some games but the people he parted his experience to.
Yes, because Daytona USA was actually Nagoshi's game.
Also Yu Suzuki's last run on VF was with 4FT.
He had nothing to do with 5 and its title updates.
Sega for fighting games at the moment is content with Frenchbread's anime fighters and Arc System Works' Guilty Gear (AC+R and Xrd) to help drive their current Nesica-like arcade download service. DOA5 is on the same service.
I mentioned this in the tekken thread, but VF has historically been a graphical showpiece for new Sega hardware. But with the current trends in download services (the modern take on SNK's MVS), and the configurations of Sega's current Ringedge line of arcade boards. It's a bit of a head scratcher right now where VF6 fits in. Also the last update announced was another revision of Final Showdown in arcades, which was awhile back.
For fighting games, unless you are Bamco, those no longer get anymore dedicated hardware and cabinets.