Feature requests:
PCI, that way I don't have to give up my current vid-card for regular PC stuff. (As long as VE supports being the second or third display under Windows [it should]) This would nullify my request for VGA output. Also would be good for those people with systems in thier cabs w/out an AGP slot.
Two connectors for video out: HD15 female w/ H and V sync (VGA pinout, switchable to C sync if possible) for those of us with VGA hacks/J-Pacs/arcade monitors that support H & V sync already. And a D9 female w/ C sync, since that'd be easier to hack (figuring out 9 wires instead of 15, or easier soldering to the male connector).
3D support! Gauntlet: Legends, racing games, 3D emulators or arcade-like games would be great to play in a cab. I know it probably won't work if the card is a secondary display, but I'm willing to reboot and play around in the BIOS each time I want to play these. Considering the 640x480 limit, 16MB of ram should be enough, but I'd feel better with more (32 or 64).
Other thoughts:
I don't think Act-Labs guns will work, since they're designed to use 30kHz, instead of 15kHz this card would output.

Would be cool though.
As far as video input for consoles, if the card is the primary display of the computer, about any TV capture card should work. I'm not sure if many cards would work with a second display.