The issue of copying other game’s assets or even remaking an old game, comes up from time to time. I stumbled upon Supercell’s “FAN CONTENT POLICY” that addresses fans using their IP to make content.
I though it was an interesting way to address this issue.
That is certainly a good way to handle things. I wish others followed on something similar. Rimworld & Prison Architect also had a small issue about assets, well, maybe issue is not the correct term. I don’t even know if legally there would have been a case, but everybody can see how similar they look if not direct copies. But the Prison Architect guys were ok with this, actually even in positive mood.
As for us… The current IP holder probably says NO 
So we just need to make sure that they don’t have a legal case.
Also Supercell is from Finland. I’m obligated to say this. Torilla tavataan!
I just think of the Skyblivion project. They are also a fan project which rebuilds Oblivion in the newer Skyrim engine, with better Assets etc.