I like progression rewards. It gives everyone a shot at a decent prize. What I like less though, is that it requires a LOT of time to reach the LT in an event. Even though I have reached the LT progression multiple times, having to play several hours each day for multiple days in a row is really something that drains the fun, in my opinion. Do you really wamt to require players to have no life outside MPQ in order to win something decent? 
So, if you aren’t able to or do not want to make that kind of investment, you always miss out on the nice things, even though you may still be playing a lot. I often find myself in the situation of not having enough time to do all that grinding without having to give up sleep/social life/work.
That’s why I would really like to see some kind of cumulative progression reward system. How to implement this exactly is up for discussion, but you could consider some kind of structure similar to the PVP season progression. Drawback: that too is something with a strict deadline, something I’d rather avoid.
Another idea is endlessly cycle through a reward tree (or different ones), more similar to the SHIELD resupply system. If you’re worried about giving too big rewards to lower-leveled players, you could consider (for example) basing the reward structure around a ‘score’ that is calculated on how strong your roster currently is (levels, covers, that kinda thing).
Lots of room to maneuver here.