If you feel a dreamcast is going to deaden that authentic arcade expierence because of these "problems" then don't use one.
Its not like a Mame cab that someone built with a computer monitor, and Lazarus front end, and bizzillion controls, and PC speakers, running off a PC is going to make it any less arcade authentic! LOL

Now that I got that out of the way, the (overly expensive) device that makes a dreamcast jamma compatible with "insert coin" msgs is
http://www.frolicker.com.tw/mgcd/mgcd.htmAs for the disc swapping...I dont see how this is a problem except for the lazy people out there. It takes me 15 seconds to open the coin door, eject the disc and put in another. Sure you could try Chancast emulator, but be prepared for unsupported games, and crappy frame rates. I find myself leaving the same game in my DC cabinet for days, v.s. playing Mame and changing games every 5 minutes out of boredom (talk about deadening an arcade expierence)!