Mmmm.. doesn't sound too bad for a one-of product. No need to engineer custom PCBs or any such stuff.

I guess what it might need is

-- a memory chip for the video ram, perhaps piggy-backed onto the existing RAM on the board (epoxy is your friend).

-- a 6845 compatible video controller chip to manage the raster scans and stuff.

-- a small amount of digital glue as required for accessing the 6845 control registers.

-- some nice analog glue to provide composite video-out.

-- some kernel mods to update the display data in the new memory chip.

Trickiest bit will be managing access contention to the video ram, or are there now commonly available dual-ported ram chips for this purpose?

As a hacker, I'd do it if I wanted something like this.

-ml