Love this mod!

But when I walk into a factory building from factorissimo, it turns the nice concrete floor to dirt. Is there any way to fix this?

Same here. Dirt replacing all of the concrete in factories.

Literally just added two lines and it's fixed.
Unpack the zip, open control.lua in a text editor
Replace everything with this

To mod author, my changes are on lines 38, 39 and 88

@Kryzeth: If it's that easy, could you publish a compatibility mod that fixes this?

Nevermind, done: https://mods.factorio.com/mod/Dirt_Path_Factorissimo2_Compatibility