This may come as a bit polemic, but hear me out – this idea is only to trigger a discussion and see what other people think. I was thinking how cool it is to feel the freshness of a wipe: starting from scratch, feeling helpless, and using everything available because it's all you got. Poorly modded weapons, cheap ammo, cheap gear – you get the point.
Now the minute you get access to flea market and lvl 2, 3 and 4 traders this starts to fade out, and as wipe progresses it is completely lost. There are many points and issues that cause this which I'm not gonna mention, but I thought of something that could make the trading world feel more alive and not make traders overpowered or repetitive – something that could help further extend this period of fun later into the wipe: dynamic trades.
Imagine this: Lvl one Prapor has a very limited but constant stock of weapons, attachments and etc. You can buy as many of them as you want, and stock is infinite or at least player based. This would remain unchanged and as it it right now. Level TWO prapor, however, would now offer A FEW unlimited supply items, constantly on offer, and now would offer single offers of items that would change in every restock. So maybe, lvl 2 prapor is selling ak-103's in this re-stock and selling a couple of other weapons on the next one. Do you like 103's? Maybe you should buy 2 or 3 just in case.
Key items such as medicine, key gear or stuff needed for quests would remain unchanged, but other items like ammo or guns would be sold randomly (based on chance tables) on higher trader levels, in a player based limited time offer sort of deal. This is more or less the way traders work on S.T.A.L.K.E.R. (at least Anomaly mod) where you go to see a trader one day, he sells some stuff, and the next day most of that stuff has changed and he now sells other things.
EDIT TL;DR: Trader offers are mostly dynamic from lvl 2 onwards. Their offers change on every restock.