I may be misunderstanding, but it sounds like you want general stores to work like they do in osrs, except you want the prices to be based off of trading post values? If I read this correctly, then I have a couple concerns.
One is market manipulation. It could be very easy for a rich player inflate the prices of something just to sell them to store.
Another concern is dev time. I'm not sure how they would even go about this, and if they had to do each item individually, it 100% would not be worth it.
I like the idea of more gold currency floating around for wells and stuff, but I'm not sure if this is the way to do it.
These templates make me cringe a bit. Especially the "is this in osrs?" question, if it pertains to changing something that's not in OSRS anyways. I'd just prefer guidelines instead of a copy paste template. I think the sticky post "steps on creating a high quality suggestion thread" is phenomenal, and is much more important than copy/pasting a template. I would like to see you fill out your own template for this suggestion, with examples.
Edit: kinda wish i saw the date posted earlier. Oops!