After working on 63 individual Halo missions, all 6 campaigns are released on NexusMods. Fixing bugs and tweaking the campaign will follow suit.
Halo XL: https://www.nexusmods.com/halothemasterchiefcollection/mods/2458
Halo 2 XL: https://www.nexusmods.com/halothemasterchiefcollection/mods/2459
Halo 3 XL: https://www.nexusmods.com/halothemasterchiefcollection/mods/2460
ODST XL: https://www.nexusmods.com/halothemasterchiefcollection/mods/2462
Reach XL: https://www.nexusmods.com/halothemasterchiefcollection/mods/2463
Halo 4 XL: https://www.nexusmods.com/halothemasterchiefcollection/mods/2461