As a Roblox developer, it is currently too hard to have nice-looking hoverable ImageButtons. The process is slightly easier with the addition of the HoverImage property, but the inconvenience arises when you want to use the exact same image on hover, just slightly darker.
My proposition is another property added to ImageButtons, HoverImageColor3;
It would work the same way regular ImageColor3 works, but applied to the HoverImage.
This would allow us to easily use the same image (less assets for the user to download), with just a simple Color change on hover.
Yes, this could be coded into any game quite easily, using UserInputService, or MouseEnter and MouseLeave events on the ImageButtons, however it would be very inconvenient and you would need to make a decently complex handler to automatically support all ImageButtons in your game.