Too much trolling, I only read the OP so sorry if I repeat anything someone has said.
The law and lore abilities you want to add are no good. Stalls have high taxes for a reason. We want you to trade with each other in person, that's the entire reason why the stalls are so pricey to run. We can't go giving an advantage like this to people who have just ground out tons of L&L. Plus, it would make people feel obligated to crank their L&L that high if they ever want to compete on the stalls since lower taxes means lower prices and no way for anyone else to compete until they do grind the points.
The tailoring idea is better, maybe. But duplicating items is a silly mechanic. Maybe add the extra slot chance and item removal chance, though that seems a bit boring and you've already improved your slotting just by getting the points.