Doing them with one character, not at the skill cap, with a sorceror suit so scaling of the encounters would, I thought, be fairly low - thankfully he is a stealther/ninja/mage, or he would be dead so many times over it would be enough to make me give up in disgust.... every creature is 95 in all resists, 151 in all combat skills, and several thousand HP (Ettins were 4.5k, dire wolves 3.5k), never saw spawn groups below 6 creatures, all move VERY fast. This is so far over the top I can't think how anyone EVER reckoned it was sensible....
If you do these trade deals with stealth you are just going to fill the world with super-powered monsters, presumably also aggressive to everyone else as well as the carrier of a trade deal, bit hard to test that one solo..... and even if they are short life mobs, the potential for making travel hideously dangerous is far too high - and if someone takes a trade deal box to a RP town (where people tend to use far from optimised gear) and hides... the stuff it spawns will be massacring most RP folks faster than you would believe...
If you want to do trade quests to benefit a city .... it's silly. You can choose which city you get a trade quest FROM, but all the benfits go to the city you deliver to... and you do not get to see that until after you accept the offer of a quest, so if I want to support my city, I have to sit there accepting and rejecting quests until I get one for the 'right' place?