Compact road cranksets are typically designed for 16T. Modern MTB gear sets are 14T max difference. In a light duty application, you could probably run a MTB FD to 16T for on-road use (low load & vibration).

Either way anything beyond 16T is going to be suboptimal. The main problem is the FD not having enough rise to avoid crashing into things.

A better solution is a wide range MTB cassette. With a MTB RD you can run a compact double (or mountain double), and an 11-36 (or even 10-42 [11spd]).