At long last an IdolMaster game has been released on Steam (a first for the franchise), making it possible to produce nude mods. Granted, the game is available only if you live in Japan (or perhaps if you use a VPN), but I thought I'd make a request for this game anyway just to see if it was possible.
No online, no gacha. Tons of DLCs.
Region Locked game, Steam pages:
https://store.steampowered.com/app/1046480/
https://steamcommunity.com/app/1046480/
Steam