you planned to add rtg support to your sdl lib, nova, remember? i think before having more ports it would be most convenient a challenge to have them run on every possible amiga config (given its fast enough). beyond that having a shared library would allow to release ports and update the lib in meantime, but might probably influence debugging even though im not sure about that.
why am i telling this? mostly for practical reasons. i have just tested grafx2 port by artur and it is not usable as it is, while it is a great program to have. im not sure on can squeeze it below 800x600 to work on aga, but even having it on rtg would be an advantage.