On SeaVGABIOS, text writing now works in all graphic modes, though not all vgabios support that. The original bochs vgabios didn't support it in "direct" or "packed" modes, and I think it was broken for years in planar mode. So, it's rare for text writing to be seen in any mode above 7. (It's also rare for anything to go into cga mode today, but for ancient programs, it would not have been unusual to write out text in cga mode.)
Ah, ok. Didn't know that. So it actually makes sense to support all modes <= 7 in sercon. 4+5 are 320x200, which should be 40x25 chars, and 6 is 640x200 and therefore 80x25 chars (both using 8x8 font). I'll go add 4+5+6 and simplify the mode number checks.
cheers, Gerd