Am I stuck trying to fit all of my stuff on a 2gb SD card, or is there a version of the file replacement code that will work with 4gb?
No.
Why hasnt anybody worked on THIS. This would solve all the Texture limits! All we have to do is hex it so that it reads SDHC! Is that so hard? (for me yeah. I suck at hexing unless theres a Tut with pics lol)
It's more complicated than that, I'd guess. I mean, the newest HBC and System Menu 4.0 and up support SDHC, but if try using an SDHC card, there are a crapload of problems with a lot of apps loading and saving. If someone were to code SDHC support, it would be tricky, and using that same SDHC card with other apps would fail. For me, 1gb is already plenty. I put all my hacks into the iso, and my SD is for testing/character hacks only.
Or that's just what I think.
Sadly, Brawl reads up to 2gb. It doesn't matter what you use outside of Brawl.