In the second screen of options there's the "Halt on" option. This sets which errors the bp6 will halt boot on, and you should be able to tell it to ignore the video card missing error here.
Hrm, I would have thought it would work then, maybe Derek could offer more insight.
Possibly an easier option would be to buy a cheap old agp card - I know new GF2MXs are only £30, so you should be able to pick up something cheap and old for less on ebay.