Personally, I think that (whilst not my absolute favourite personal suggestion,) Castlevania Warriors would be a brilliant example of this sort of thing. Likewise, I think that Mario, Kirby and to an extent Sonic could work here too. As for other series... not gonna lie, it would be really cool to see how a Metroid Warriors was handled with various Hunters playable, but it wouldn't really fit the series. Final Fantasy is an obvious choice (Add Crono as DLC!), Xenoblade seems like it could be cool? As much as I'd personally love to see a Mega Man Warriors title, I feel like it wouldn't be popular enough to warrant release. Likewise, Pokemon Warriors sounds like it could be really cool, but I have a feeling the "weapons" system wouldn't translate well...
god damn this series has so much potential