Rather than limiting their recipes with town tier, I feel like the inventory of the Market Stalls them self should be limited by town tier.
An example only to serve as an example and not the real deal: Tier 2 allow Market Stalls to (possibly) sell metal bars - Tier 1 Market Stalls are not able to sell metal bars at all.
I really like the idea about merchants in general taking longer time to return - perhaps there’s even the possibilty to have some merchants (who sell more valuable stuff) to take even more time to return, too.
My idea was to add specialised traders with stalls requiring the basic stall, crafter’s sign and some resources to be crafted with return time of a week or two, but this requires to have one timer per trader so one doesn’t abuse it by placing multiple stalls.