I am in 2 minds about this. It sounds good on paper but imagine trying to collect multiple sets with the stash tabs we have: 1 personal, 3 shared. It is already a nightmare just keeping hold of decent items, runeword bases, perfect gems and runes with that limit. Now add the collection of set items to the mix. I have no more slots to make any more mules, where would I collect them? I am weirdly kind of glad that most set items are garbage, because it saves me a ton of space.
Now if they want to give us more stash tabs at the same time…