How fun! Feel free to do that.
The textures are available in the zip file with the game executable. I think the sprites may not be the best suited for a grid, since their sizes aren't clean ratios of each other, so you would probably want to edit them a bit as well.
It would be far down the line, but if you should get around to releasing it, you can link it in a topic here and I can pin it (just don't charge any money for it or anything).
Best of luck either way.
Also fun coincidence, the last few months I myself have actually been working on a factory builder in godot, and I ended up deciding to use a grid this time. I have really changed my mind on the idea of a grid, it's the best invention, and it's really good for literally everything.