If you could be a wizard Harry, what kind of progression would you magic wand to Halo Infinite? I agree with you btw, but I want to see if we're thinking of the same kinds of stuff.
Rather than having shitty weekly challanges that everyone hates with a time limit, I would have multiple rewards locked behind specific challanges accessible at any time, finishing so many games with a 3-1 K/D, getting 5 roadkills with a warthog in a match, get 7 head shots in a row with the sniper etc. These would be accessible to any player at any time. Some would be relatively easy, some would be very very difficult. But the idea is to have a spread of rewards player could work towards by playing multiple modes. They would be set in blocks with a unique special reward if you clear every one in the block, clearing all of the blocks would reward something very special, recon helm special.
Outside of that I would badge onto the rank system introduced in season 4 to unlock new armor sets and accessories similair to reach as you progress, with higher levels giving you more cool shit at you progress to customise your Spartan, probably something big at the start of each tier like a new base core that builds up as you go up that tiers ranks.
Just standard stuff, give players something cool as they play, but also give more hardcore a bunch of challanges they can actively work towards at any time.
Finally I would make a new core that specifically links to campaign and all the achievements there, give free 2 play players who might not be interested in the campaign otherwise an incentive to check it out and complete everything it has to offer and be rewarded for it. Yeah sure most people have gamepass and get this anyway but might sell a few campaign this way.
As for MTX, rotating store can go fuck off, keep all the event shit in there but let everyone buy them when they like, a full listing all the time. All Past battle passes would be buyable at any time and you just work on the one you want at the time.
I think that's fair, they still have a cash shop, they still have battle passes, just players have something to work on outside of that, and they can buy the better looking versions of the event armors when they pop up if they want to support 343.