An update: I finally managed to get Mameboy compiled. :-) Adjusting the screen was the easy part. I had a lot of trouble trying to get things to compile! Part of it were compiler settings that were off (such as the directory paths). Also, a lot of it was just me getting to understand the organization of the code, but part of it is something odd about how the compiler decides what and when to compile (I would get tons of linker errors, go back and force things to recompile in a certain order, and it would be fixed). (I prefer old-fashioned makefiles where I can explicitly tell it what to do...) Anyway, the important changes were the key mappings and the hardcoded settings in the screen initialization.
If y'all would like, I could put my changes into #ifdef's, and that way it could get into other people's distributions. (Currently, that would be Mameboy.) However, I need to play with MameCE3 more to see if I can get that to work; I don't think WinCE 2.11 likes the "gx.lib". Meanwhile, it's nice to have something running. :-)
Thanks for the help!