If Daniel pops by Amselfass, please tell him I'm burning with desire to help with the translation.
I really like the moneylender notion, BT, and the more complex product chains seem cool. I'd make loans and managing them a sub game of its own.
My thoughts would be, more or less in order:
1) Much stronger macromanagement tools would be great, like an estimate of the amount of goods a convoy needs to deliver to a town per circuit to satisfy its need during Auto-Trade setup.
2) Sliding scale wages for workers. If wages are high in a town, prices and rents can go up in response. New Workers will be more inclined to migrate to a town with higher average wages. Give each class of workers in the city as well as the Burghers and rich folk an average purchasing power. If you really want to get fancy, perhaps the supply of savings can effect the interest rates available at the town's moneylender.
3) Finite Gold/Silver supply. If more gold flows into the town by running a massive export/import surplus with the rest of the Hansa, the AI will be more inclined to increase wages and rents to grab that cash, prices will go up for imports, and the balance will restore itself.
4) Variable Land Taxes for the above reasons, since if the Cost of Living goes up, troopers will want raises along with everyone else. You do not want underpaid troopers.
5) Anything even remotely like a tech tree has no business being in a Patrician game.
6) This is probably wishful thinking, but it would be awesome if there could be a province map for each town's hinterland, kind of like Caesar II, where all Agriculture and Mining needs to take place. This would make sieges that much more dangerous, give the local Princes bases of operation, and have outlying villages where raw materials would accrue and extra finished goods could be unloaded. It would also make roads actually MEAN something, along with canals and less navigable rivers for barge traffic.
7) This is ahistorical, I believe, but it would be awesome if the Hansa towns could take the fight to the Princes, and take over their lands like the Italian cities did. There could then be a mechanic for feudal taxes in the hinterlands coming into the towns and their expanded militaries, the same tax structure increasing the power of the local lords when they are in control of these areas. The power of the Crowns would then become important, since you'd need at least their indifference to take down local lords or face REAL retaliation. Thus it'd be one thing to expand your town's power base around Luebeck or Novgorod, but insane around London or Stockholm or Oslo.
Likewise, permanent Tax obligations to local lords or royals would be an interesting long term penalty for losing a siege.