While I'm all for solutions that address causes and not symptoms, I hope nobody seriously believes that TIME gating would be a good solution. It;s why nobody does PP. I don't grind, but I accept that some do, and I would like to have the option of grinding for something that I want to complete fast and not know ahead of time 'when' I will get it and that's all that matters.
Don't get me wrong, I'm all for the nerf (as long as it is appropriate) but dead against time gates. Skill should always matter more than patience.
The problem here was not rep rewards across the board, but rep rewards vs effort. Data missions should never have given so much rep. Killing 6 known terrorists though? Absolutely that should make a huge impact on your reputation. You are a killer of terrorists!
It's always how you design it. I think most are fine with steady progress instead of instant access and gratification if:
The path in between was more rewarding.
There is a reason "milestones" are a thing - you can rest there. Take a look at the next leg of the journey, prepare and equip with new stuff you just unlocked. What if the different ranks rewarded equipment? Equipment that has you play with it. Expand on your game and experience.
Example:
Warframe has "factions" you can earn and trade in "standing" with. Earn enough standing and you can rank up with them and unlock gear. Now, many of the factions and gear stuff don't interest me but there are a couple that have interesting pieces. If you want you can pick a faction and shop there, the daily standing earnings are capped so no unintended bug should allow for people just beelining to the last rank.
Which has mostly cosmetics, a couple of mod cards that usually DON'T overpower a Warframe - just tweak it's gameplay an interesting bit and weapon variants for completionists.
Usually you pick one or two to level - earning standing with these puts other factions at odds with you, because politics and if you annoy a faction enough they send out hit squads for you - nothing ppl can't really handle, but a noob might run in problems here.