Well, i'm not sure, but there is no way to downgrade to 1.5 that would enable you to play Homebrew and Iso Loaders. But you can play almost all homebrew games with the GTA Homebrew Launcher (there are several versions of it), but you can't start Iso Loaders. But since you only want that Emulators, that's no problem.
Just get GTA, and the GTA Homebrew Launcher. Most of the Homebrew apps/games work already with the GTA Homebrew Launcher, but not all, and no Iso Loaders.
Anyway, perhaps there IS a way to downgrade from 2.01 to 2.00 and then to 1.5 or directly from 2.01 to 1.5 - but i'm not sure...so rather wait for other answers, before getting GTA, just in case you don't have it...well, even if you don't have it, get it, it's cool!