A way to preserve grasblocks so that they are not affected by pathbuilding, kind of like the new waxed copper mechanic in 1.17, for decorational building purposes.

Ok so I'm thinking about a "Lawn Block" which is craftable and have the same texture as grass block.
1 Dirt + 1 Bone Meal gives you 1 lawn block.
1 GrassBlock + 1 Bone Meal gives you 4 lawn block.
This is what you're thinking about ?

Yes! Exactly what i was thinking about.