Still think an Indie rep of some sort could help explain the sheer secrecy surrounding #5.
The smaller the company, the easier it is to keep tabs on the employees and make sure nothing leaks. And, if leaks happen anyways, to narrow down which employee is anonymously leaking information to people like Verge/Sabi/whomstever, which might be why those leakers claim their sources are so very, very skittish about telling them #5's identity outright.
Also, indie studios are frequently one-hit wonders. They have one franchise that hits it big, and nothing else they're really known for. So giving away the company would end up being more revealing than for a bigger corporate entity with a larger portfolio of games. For example, "Capcom rep" gives lots of options, but "Team Cherry rep" is synonymous with Hollow Knight.
The only problem is... it's difficult to predict which indie studio/character/game would get prioritized over the ones that already have "lesser rep" in the form of costumes, spirits, and trophies. Unless they make an exception and break that "rule" for the first time... and the only one of those three indies I can see
"breaking" that rule is the one that's not represented with its actual protagonist.
Hope I'm able to contribute to the discussion a little. I would very much like some of the characters already tossed around in speculation, like Phoenix, but it feels like it's only a matter of time before every character people are already talking about gets deconfirmed some way or another....