One great way to reward players for achieving milestones and continually returning to the game would be battle-damaged cosmetic rewards for all factions.
Helmets, torso, and pants cosmetics that are torn, dirty, and/or damaged by combat to really show that your squads have seen a thousand battles instead of looking clean.
Methods of obtaining these cosmetics could be simple:
- Late stage progress in the battle pass
- Late stage event rewards
- New Achievements/replacing some of the more difficult achievement silver rewards
- Could be rewarded for completing all researches in a tier for each faction
- Could replace some of the Battlepass season high rank rewards
- Replace call sign orders in the veteran box
The idea is you have a lot of avenues of getting these cosmetics and you slowly accumulate them over time. So that as you progress through the game your squads can look more and more like combat veterans to reflect your progress.
The cosmetics themselves are not so destroyed though that they standout too much, they just give your squad a more worn look.
The rewards would not be frequent enough to be too annoying to people who may not want them, replacing small silver gains or other unpopular orders.
Battle Damage by Oliver Lock & Daniel Fisher is full of examples like these to draw from!