Will try MoP, until now isn't working. The problem with empty slots is that one artifact will move in a combo place, because it reads -1.

Let's say you have admiral hat, so head slot returns combo on, but neck returns -1 (empty). So if other hero has something on neck and you press to give artifacts, his artifact will install on your neck, but you keep admiral hat too.

You can see that when you hover mouse over combos. Except one slot, mouse says "empty" on all locked slots.

Solitaire code: no idea how to use it. Jim uses it for active hero without specify ID, but in transfer artifacts, there are two heros active. Not working.

@Edit: backpack redraw solved with MoP code.