Hmm 512mbit, pulled apart the rom and it seems you only need to lose a couple of hundred kb to get under 256 and the extra languages seem to be a good possiblity: maybe a rip similar to the Eu nintendogs ones, I will try and test later today along with the Japanese sound replacement.
Edit for a 256rip check the DS rom ripping link in my signature.
@Zaraf there are nods to previous storylines and various characters make cameo apperances/redeem their roles but 1 is pretty much the same a 6 bar a few battle additions in terms of gameplay.
You can play that game without playing the older versions but its not a bad thing to play the others as well.
You just beat other opponents all the time ... and in the later versions like 5 they sometimes reffer to what (*arg*) Lan did (i hate to use that damned english names) with the WWW and Gospel and so on ...
P.S is Rockman.exe 5 DS diffrent from the GBA version ?