Having Firefox would be nice although OWB does it very well ATM. I guess that when the Friedens get it working on OS4 someone may do a port to MorphOS. I think most of dependencies are already ported. nspr & xpcom would need some experience with MorphOS but most of gui part should be directly portable.

The only amiga stuff that would be ok would be ARexx, choosing screen, using MIME to open downloaded stuff if you doubleclick it as if you were using ambient, clipboard support and ASL requesters. Perhaps fonts preferences. Rewritting the full GUI using Reaction or MUI would be a complete mistake IMHO. Just look at Mozilla menus... Mozilla menus seem to be better than intuition menus (e.g. allow multiple levels with drag'n'drop, pictures...).