What if ordinary merchants were no longer perfectly happy to purchase your junk.
It would be annoying and pointless, that's what. This aspect of the trading mechanic is fine as it is, and there's no need to change it. Just because you can change something doesn't mean it's necessarily a good idea.
But I would say that the issue with some items being more expensive than any merchant can possibly buy is rather absurd, and needs to be fixed. Either there should be some merchants with enough gold to buy the most expensive items in the game, or the price of high level items should be lowered to a level that someone can reasonably afford. An item's value is not some metaphysical attribute of it that everyone knows, it's the price that people agree the item is worth, so if an item costs ten thousand Septim's, then there must be SOMEONE who can and is willing to pay that much gold for it, and it's certainly not the player since, with some very rare exceptions, the most expensive items are not ones you'll find for sale in stores anyway, at least in Morrowind and Oblivion. If there's an item in the game that costs twenty thousand gold but no one can afford to pay more then two thousand, then the remaining eighteen thousand of its price is nothing more than decoration. Not that I'm saying every NPC should be able to afford my ebony armor, obviously, the amount of gold NPCs have should reflect the sort of merchandise they deal in and the sort of person they are. A food merchant in the slums should of course have a lot less gold than a smith in a an upper class district who deals in high-quality weapons and armor, I'm only saying that the game should adhere to the basic principle that if something has a high value, there should be SOMEONE who will pay that much for it.
I'd also say that you should occassionally be able to find higher level items in stores. Because part of the reason for players having a lot of gold and nothing to do with it in the Elder Scrolls comes from there being nothing worthwhile to spend gold on in the late game, since nothing you can buy at that point is worth using. If you could find some of the kind of items you might want to use then for sale, then maybe you'd have a reason to spend all the gold you have on something. Like gold, the kind of items a merchant can sell should depend on the location and quality of that merchant. You shouldn't find a merchant selling glass armor in a place where people should barely be able to afford steel. Alternately, Bethesda could do something like that smith in Tribunal where certain characters can make high quality equipment for you, for a price. This is actually probably the most logical approach, since it's mostly only special customers who could afford items like that, I'd think, so it would not be unreasonable for smiths to only provide them through special commissions.