I don’t really support this because there is no real reason to uncraft a higher tiered cubelet. All the good stuff comes out of the Ubers and supers (mainly), so crafting downwards provides no benefits. And for the completionists, you get way more normal cubelets than supers and Ubers so you would collect all the commons and uncommon sway before you get all the legendaries and mythicals, so you might as well just put those few ubers you get from your rank straight to that.
Another reason is that it would just add another item to the endless list of development. It is never a case of just typing in two lines of code and being done, though it would require much less development than adding a new game (obviously). I just don’t think it is worth the development time. Could be doing other things like bug fixing, or working on whatever other item on the list.