This is all, at the end of the day, a moot issue. WOTC will never make any format a proxy format, and you are already perfectly welcome to make your own tourneys with your own rules as it stands. Sanctioning is really the only thing that differentiates this.
There is a better chance that at the end of the day WOTC just stops supporting vintage and gives it to the players to run, which is in my eyes the same as just killing the format.
All of this is just trying to come up with answers to the other intractable issue that is causing these high prices, which is the reserve list, which will also never go away. There are some cards on that list you can likely remedy like Bazaar, tabdernacle, etc by just making them legendary snow or what have you, but you will never fix lotus or moxen without creating lists that attack on different vectors like dredge or some sort of null rod list that wants no moxen or lotus.
let's say the replacement card is good enough, dredge is still a competitively viable deck with 1 bazaar and 4 of the new card, and needs no other reserve list cards- I think bazaar just hits 3 grand in that scenario
I'm not sure why you think that. Right now the cost is 100% driven by lack of supply and the fact that you need 4 of them. If you literally quadrupled the supply of available playable sets I really cannot imagine the cost skyrocketing. I don't think it would precipitously drop, but to increase immediately after a ban seems counter to how we know the market functions. It also runs in the face of the price of things like moxen which are more prominent in more decks and do not even carry that price tag. If anything it's price would be closer to Library of Alexandria, which is another restricted reserve list card of equal rarity from the same set which probably sees about as much play in this scenario.
restricting bazaar for price reasons is also just a bad idea for the obvious reason that bazaar allows the only viable deck to exist for less than the cost of a lotus, which every other deck needs, most with quite a few moxen. It's not easy to make a hatebear deck that doesn't want lotus and on color moxen, even with null rod effects in it.
I don't think you can restrict it without a replacement, because unlike shops there is no Tolarian academy or Ancient tomb for back up. I suspect that in commander product or another Horizions set you could get away with printing a legendary land that had some sort of looting ability on it that could function as the new bazaar without breaking legacy. It would depower the deck to some extent, though at the same time it would be similar to how shops gets in effect 5 shops when you count academy. Frankly I think we take for granted the fact that dredge needs no mana now, I wouldn't even be against forcing them to run something like faithless looting and mana, but you would have to restrict MM in that case.
Restricting shop for price reasons is just a joke, as a shops deck has over 10k in non shops cards in it given lotus+moxen alone.
Shops should honestly just be restricted though, price point and this topic aside. It would at least open up the supply of the card for higher end commander players while also helping tone down the most problematic and costly list in the format.