Will unlocking the national dex early in Emerald break anything?

[WraithTDK]

I want to use Pokémon Emerald with Pokémon Box, and I don't want to wait until I've beaten the Elite Four. I honestly think it was a silly requirement to begin with. If I unlocked the national dex early (which I think can be done by marking Mew as seen), will it break anything in my playthrough? If so, could I just check Mew as seen, and then uncheck it to "re-lock" the national dex just before facing the Elite Four?