[icebraining]

>maybe the would need to be a time limit within which the mouse couldn't be captured again

Why not re-capture only when the user clicks on the game again? In fact, I don't think the permission bar is needed at all, it would be implicitly given by clicking.

Of course, ESC should always work. Which would actually work fine for most games, since ESC presents a menu where the pointer isn't supposed to be frozen anyway.