I ran this exact setup with the GX crankset. It is an excellent idea. Go for it.
Some people will claim that the 36-11 top gear is not fast enough, but in practice I almost never used this gear. Maybe five times a year max. I'm not strong enough to push this speed on the flat, and on downhills if I'm going that fast I'm already coasting.
I did use mountain derailleurs however. You'll want to check the compatibility documentation for your derailleurs to see how much range they can support. Personally I don't think the 48/31 GRX crankset is a good solution. It's barely lower geared than what you already have. What's the point.
Last edited by Yan; 07-28-22 at 03:46 PM.