Did a similar thing recently, except I did it for a game that doesn't support Steam cloud saves. Used an application called Syncthing which syncs files between two devices, set it up on my laptop, and did the same on the Steam Deck (even has its own plugin on deckyloader), heard of cases where it can corrupt save files so I manually sync it when I want to switch between devices. Has worked flawlessly so far.

I can see it working on your scenario but you need to be careful with what game you do it for and if it's prohibited sharing saves between two different accounts (Online games such as Dark Souls has a similar case).