Hmmmm. I would pay full price for Reach, and ODST campaigns, firefights if they add them as paid DLC later. With all the same perks. Achievements, forge/theater/60FPS1080p and some little tick box to allow them in map rotation. Reach has 17 Multiplayer maps by itself, and then it's own Forge guidelines.
If you want to tell the entire Master Chief Saga, these side stories would be great to have added later. It's almost more about the idea, that I can get everything from one disc. That I don't have to purchase another collection, or updated extreme directors cut blu ray ripley scotts ball sweat edition.
The package is called Master Chief collection, but in reality Halo 1-4 is about Master Chief and the covenant war. Or at least Halo 1-3. Halo 5 marks a new protagonist, new enemies and dilemmas. Reach is a precursor to Halo 1. You need it to literally understand the proper context of Halo 1. ODST is basically filler for Halo 3, it won't make much sense by itself.
And Halo Wars is like the epilogue to all the games. Halo Wars would have to be it's own mode haha. It would be weird to be playing online and then have everyone vote for next map being Halo Wars.
But I think they would fit. With that much variety, you literally might never grow bored. The sheer variaty of such much maps, wow. And seven campaigns. It literally would allow Halo 5 to be a new beginning. And would probably render the need for future remakes, Anniversary editions needless. The final swan song for Halo. Letting Halo 5 actually become something new instead of this schizo child that is stuck between being familiar and new.