Earth Defense Force 4.1 is not a bad guess, but I kinda hope it's something else because we already know about that one through the Steam database leak. 
This, so technically it could be anything, although some bigger devs/pubs would probably handle it themselves.
Nah, that's wrong. I'm sure they get requests for tons of stuff.
Sure, Platinum games would probably be up there, but I could think of lots of games.

Ghostlight doesn't have a connection to anything, they don't own IP, they are a localization/porting house.
This, so technically it could be anything, although some bigger devs/pubs would probably handle it themselves.
If it's not a Platinum Games title, how can it be a "highly requested" action game? The only highly requested action games for Steam are literally just those.
As a result of that, I can't even guess.
Nah, that's wrong. I'm sure they get requests for tons of stuff.
Sure, Platinum games would probably be up there, but I could think of lots of games.