If you want to make it interesting, make it so that you can lose your shirt doing it.
First, make it largely automated.
Second, make it menu driven.
Here's how it works...
You purchase Caravan Carts with CROWNS, the first one's cheap. Only ten crowns. But they go up... steeply.
You can Garrison units inside your Caravans to defend against interlopers. Some units are better at defending caravans than others. Mounted Rangers might be the best for Elves, for example, as they are ideally suited to skirmishes. Every time you add a unit to the garrison it costs you a crown. So if you send out six dudes and they all die, it'll cost you six crowns to re-garrison etc etc...
And you're doing all this because there's a good chance your caravan could be lost. The Caravaneer only hears of it later in message form, or somesuch "Your Caravan was despoiled by orcish raiders!"
On the minimap there appears a marker for where your goods are. You have twenty four hours to launch a party, overcome the raiders defenses in their raider hideout, and take back what was yours.
You'll never get *all* of it back, you'll just get *most* of it back.
In addition, when you're setting up your routes you get information on what's going to be going on where you're sending your caravans... nothing specific in terms of numbers more kind of like afternoon weather reports. "With an increased chance of raiders, and malignant weather Ral Nistro is hurting for wood, stone, and food".
This of course means you're more likely to lose your proverbial shirt but sending your crew out there will net you more money.
You turn it into a slot machine.
All of this nonsense is situated so the player won't realize that although they will be seeing returns for their investment your manipulation of the numbers ensures it doesn't become insane. Something like a 15% return...