Its for this particular reason why the Amiga failed (3rd paragraph).  A browser for 3.x based systems?  Oh god, please, MOVE ON.   Ditch those old, under specced systems.  
Support whats there.  Sputnik?  Maybe give him some more $ to port that to OS4 (if it isnt already), setup a bounty for THAT project.  Help a browser that exists NOW to advance the real operating systems that are in place, not some ol-timey rinky-dink system.
Remember Amiga games?  What, do you think everyone ran A500's w/512k ram?  Try A500 w/1,2,3 megs, A2000's with 8megs, some with graphics cards.
Good luck, this project will never be completed on a 3.x system.