Just to brag about it, did it 10 years ago: https://github.com/ponsfrilus/arch-novnc

I did a similar thing some years ago, when trying to hack my own cloud gaming setup by using AWS GPU Linux instances. While it worked the price per hour wasn't worth it compared to just buying a good GPU.

My idea was very similar, using TigerVNC and just launching Steam without a WM. Unfortunately I think I lost the code for it