CDF touring build with mtb crankset and road shifters
What you're describing is a &quot;mullet drivetrain&quot;, that is, road shifters with mountain derailleurs &amp; gears. There are a lot of variations on this. Here's a guide. Note that some   of these require third-party adapters to make them work.
Some of these permutations offer a lower gear than you might need or want. Another alternative would be a gravel drivetrain. Shimano's 2x11 GRX, for example, could be used with a 30x46 low gear, which is very low for riding on pavement, even fully loaded.