Hi and welcome here. I had in mind something similar, i.e. using gap % and not time. I finally did it following your message. There is now a link on top of every regional
closed leaderboard:
View attachment 873908
->
View attachment 873909
That already the case: the K' Speed Score disregards your worst times, so if you progress, your oldest time are or will eventually be ignored.
I saw all your times on your page from last week, maybe you checked this too early today, before the closed leaderboard being auto-archived. It occurs during the middle of every Monday morning, European time (CET).
This already exists but is not explicit:
View attachment 873911
Here the score lowered since the previous week of the last played week (this is not from your page).