At the risk of inciting exactly what Legacy doesn’t want (and I’d pray that you respect his wishes and not turn this into a wish list thread), I think this is a clue in itself.
I think this is a house from the past, like JJ591 suggested.
It would fit perfectly with the theme of being a “retrospective year”, too, with two houses already dedicated to Icons and (S)Cary, and the other houses we (think) we know tied deeply into event lore (scarecrow spiritual sequel, universal monsters, long-time wish list items) ... so I speculate that this would be an untapped theme not covered in the other houses. And IF Legacy had said that outright, it certainly WOULD lead to a long tangent of wish-list houses that nobody wants to read about.
It COULD be an IP, but I take Legacy’s comment to mean “some rights holders are hesitant due to COVID”, though I suspect it could be read in the other way. I do know that Legacy’s talked about the IP well running dry, which to me contradicts with there being “dozens” of possibilities. But I won’t speculate on a theme or past house further, due to Legacy’s wishes.