So this has been discussed quite a bit already on Reddit and other platforms.
Changing the rank rewards system from the final rank a player achieves at the end of the season, to the highest rank achieved anytime during the season, will increase activity by quite a bit and help keep the player base a lot more active, which is very important for a small and growing game like AOE4.
On the other hand, the current rewards system tempts players to stop playing once they hit their perceived maximum rank.
This was especially noticeable at the end of Season 3 where people got to their highest perceived rank and stopped playing there in order not to risk losing the rank and consequently the rewards. Going from ranked to quick match is always tedious as the map pool is very different, and the elo matchup’s are usually not as well balanced as in Ranked. Also people play a lot less seriously which puts you off the game, ultimately resulting in much less activity.
Also, the current system encourages people to create multiple smurf accounts in order not to risk their primary account from losing rank, and therefore demoralizing players in the lower ranks as they get stomped by smurf accounts towards the end of the season, thus compounding the effect.
Overall, I see only positives and no detriment at all to the game changing from rewarding final rank to rewarding highest rank during entire season.
Small but impactful change.
Just my 2 cents.