99 % of those 'hack ideas' are Nintendo related.
No idea for a good Genesis hack ?
My post from a few pages back:
I'd love a level editor for Monster World IV (or III, or II). Other features I'd hack into MWIV if I could:
-Allow for revisiting beaten areas
-Let Asha keep running when moving between screens (currently she stops so you need to double tap again)
-Set running to a button instead of double tap
-Add some momentum to the jumping mechanics (longer jumps when running)
-Re-implement the equipment system from the previous game, so you can switch between different gear without replacing it in shops
-Add more hidden stuff (hidden money in certain spots similar to WBIML, cracks in walls, hidden doors in the background etc.)
-Make the final boss tougher somehow