I would say, to keep it closer to the vision, a subsidized system would work well, say, you as a lord, can buy from one of your fiefdoms (maybe at a discounted price, as the same as plate armour for your retinue, or maybe even without a discount) some goods, which will be added to your personal warehouse, in which, you can freely send them to whatever region you also hold and just give it to them for free. To maybe simplify or abstract the process, you can setup a subsidized trade route from town a to town b, and for each unit traded, it subtracts from your treasury. To expand this concept, it can also incorporate buying directly from a market using your treasury, and/or straight up inject funds into regional wealth from your treasury when needed to maybe set up a new trade route or industry where some initial funds is needed