Mega Man 1 GB: Add more room in the robot master rooms especially with the final four. Seriously, it's so tight to move around in those rooms that it is literally impossible to fight these robot masters without taking some damage.
'tis because the GB screen was so small, and panning the camera to make bigger rooms would be absurd. personally, i think that was the charm of the GB series. when enker got a bigger room in MM10... whoa, boy... on a similar note, attacks like the rolling cutter had their range reduced to coincide with the smaller screen.
as for what i would change, i'd make MM7 and MM8 8-bit, but the FC projects seem to be doing that just fine.
in MM1, i'd add time man and oil man, remove the point system, revamp the stage select screen, and make a portrait/map of wily castle, as in the other games.
in MM10, i'd give quint a special stage. yes, quint. the poor guy is underrated atm.
and most importantly, i'd get rid of MM&B altogether. i just don't see it, or any of it's original robot masters, as canon.
Still it seemed like the bosses were harder to dodge in the first one than the rest of the gameboy games, I'm not asking for really big rooms like in the nes games just slightly bigger rooms for me to dodge their attacks o~o. Capcom somehow made it work after the first game.
Also I would give a special stage for Terra too, since he is kindof like the megaman hunter of Megaman V as Quint is to II. I mean his weapon is Sunstar's weakness, and you don't have to play an entire stage to fight him. Not to mention, Terra is like the only Stardroid other than Sunstar to talk in this game.