Perhaps we would have more of a chance if we make a collection of international differences in checkmark designs and propose that set of glyphs as a whole.

It doesn't seem like anybody ever filed the paperwork for it. (A search for "krul" on site:unicode.org doesn't turn up anything.) Unicode symbols don't just magically appear! Somebody has to do a bit of work to make it happen. If you're frustrated by a missing symbol, that somebody is probably you!

I am quite sure it has been submitted and rejected before although indeed in my short search just now I couldn't find evidence for this statement.

Edit: Seems like the earlier attempt stopped before ever getting to the proposal stage, maybe it is worth pushing through even though some of the requirements for the unicode standards can not be met.