Well, this isn't a suggestion for a Wii homebrew app per se, but a way to make another program compatible. Ya see, Timesplitters: Future Perfect for the XBOX had a PC utility released that could create mapmaker files and load them onto the XBOX internal memory. The Gamecube version? No such luck. The reason I ask is because the XBOX version's PC utility has no limit on memory when creating a map, and that would be useful to have for the Gamecube version too.
All versions of the mapmaker (on consoles) are virtually identical, so the only thing the program needs is to be able to save .gci or .sav files that a homebrew app like GCMM could load onto a Gamecube memory card.
Probably a far-fetched proposal. If you think so, just ignore this. Still, I'd like to know if it's possible.