It think this would be a great idea,
it would give other knights a chance to stake some crowns or energy so they're able to put their 4 or 5 star weapon on the auction house
They could have the rates according to stars,
To keep it fair, they could just make it so that when something is 'unbound', its level (reached by heat) would be returned to one, or have it so that if it was past level 5, it would return to level 5, or if it was 10, make it 10 when unbound
I don't know, just in general, I think the opportunity to unbind things would be good.

Another idea would be that weapons could have a chance of developing unique variants when they reach levels 5 and/or 10, regardless of the star