why implement a different vga card ?

Why not?

apart from fixing 3 buggy games it doesn't add anything new/useful to dosbox.
or the banked modes should result in faster stuff, but i doubt that.

Isn't it good that he made DOSBox more compatable with old games? I thought that's what it's goal is.

From the DOSBox readme:

While we hope that, one day, DOSBox will run virtually all programs
ever made for the PC...we are not there yet.

You sound stubborn...

I think what Qbix is saying is that implementing a new video card for new games when the fixes could be included with the current video card is a waste of time.

Ah, well that is a better argument. I didn't know whether the problem was due to the hardware being emulated or the emulation itself.

I knew I will get in trouble mentioning video in my first post. My original question was not SVGA-related. That's only that the most common hardware using this MMU feature (separated read and write mapping) was SVGA chipsets. You want something different? All right, some SCSI adapters, video grabbers, all kinds of proprietary hardware somebody may care about and attempt to emulate. All I was asking or rather suggesting was some extra flexibility in the core, and that without compromising performance.