Taking PO down a peg has very little to do with where other decks are in the format.
It has much more to do with peoples' perceptions that PO is doing something too broken, too uninteractive.
It is a subjective view informed by play experience, not an objective view based on metagame share, win rate, or top 8's.
Elevating other decks doesn't change how interactive PO is. Your suggestion is really just going to tick off the people that have a different vision of the format than you by promoting more of the types of games they don't like.
Fwiw, I do not believe any card needs to be restricted right now in Vintage. If you feel you need to address something in PO, I would recommend PO itself - Opal has been seeing play in some fringe strategies like Welder/Painter/Emry/Urza that are new and fresh, but get crowded out by hate directed against PO. To be consistent from an interactivity perspective, you should also hit something in the various Bazaar decks like Hollow One as they are perhaps even more consistent at generating the type of uninteractive games that PO gets a bad reputation for. It boils down to this:
Me, Steve, and Brian:
- Unban Lurrus,
- Unrestrict Windfall,
- Unrestrict Seal - (Not sure if Brian agrees on this, I don't remember for sure).
- Restrict Mox Opal
- Restrict PO
- Restrict Hollow One
Somehow I'm the minimalist on restrictions...
I must stress that under no circumstances should Gush be unrestricted in Vintage (with or without Fastbond). Mystic Sanctuary has put the final nail in that coffin.