The way MMR is structured currently (ie. slightly broken), it seems like the very top get a chance to “float” away from the pack unscathed and can remain there as long as they maintain a certain score.
Your proposal would seem to continually to favor those people.
A better tweak would be to take your accumulated score (ie. wins) for the week and reward people for that. Than reset that number after the rewards are handed out.
Also, you need to be interested in it. Because it’s currently the most generous rewards in this game. If you reach 2500, you can rack up about 1200 in HP and nearly 10,000 in ISO (assuming you sell the covers).