Ai display a copy of the currently selected tool in each custom tool panel a user have. This is distracting, eats up space, and serves no practical purposes.

Yes, I kind of understand the logic behind this... 'what if a user does not have the currently picked tool in any panel now displayed? how can they know what tool is no active?' — but why EVERY panel? Choose one. Or let the user to choose one.

You are allowing to create toolboxes with no fill/selector stroke, without Draw modes even (Normal/Behind/Inside) — something a user can’t get anywhere else if it’s turned off! But here you are pushing the active tool way too much.