Starcraft
Starcraft wouldn’t fit into the typical kind of Musou adaption we see, but would be interesting nonetheless. The highly futuristic sci-fi setting is something virtually unseen in the Warriors games, and Starcraft has enough units focused on close-quarters combat to make it work.
The three different factions of Terrans, Zerg, and Protess could definitely make for some dynamic and massive battles. Powerful heroes and villains like Jack Reynor, Zeratul, and Tychus Findlay could each come with unique move sets, support bonuses, and special abilities. There are some easy ways to put an emphasis on things like capturing bases or holding points on a giant Musou style battlefield. Plus, there’d be few experiences better than mowing down hordes of soldiers as the Queen of Blades.