This comment is unrelated to your leech-suggestion, but regarding flags:
Defining your own categories with named flags is such a nice idea and I believe the community would benefit from it, e.g:
However, since Anki tends to stick to a more generalized approach and I (and probably some other people) use the flags for new reasons almost every time, this seems like a classic case for an add-on.
But maybe I’m wrong and @Rumo and dae come up with a smart solution that would work on mobile too.
More than four colors sounds really helpful too and it was requested some time ago:
A greater amount of flags entails a slight usability cost on flagging during review, though. 6 colors would be the sweet spot, imo, but such decisions probably require a community poll.