Halo 2 has waaaaaaaay less powerful modding tools. You won't be seeing a Halo 2 overhaul on this scale for a long time, if ever.
Before Halo 1 OpenSauce, Kornman00 and FieryScythe were already working on opening up the H2EK, similar to how they had unlocked the HEK. They eventually stopped because, despite all the nice features, it was just taking too long.
Halo 2 supports a lot more cool stuff than Halo 1, and while OpenSauce has allowed for more cool stuff (like vehicle boarding and more particle effects) in H1, it doesn't support everything that Blam! 2 had.