Hm! This is a fun thread. I'm going to leave out Spidey rogues entirely because I could do an entire list of just them. So I think I'd go...
1. Comic Mandarin: I'd venture to say this is probably THE biggest foe that's not been made by Hasbro yet. I mean, this is Iron Man's archenemy. I suppose it's possible he potentially could be deemed controversial or "dated," but I don't think he's offensive IMO. One thing that's difficult with Mandarin is he doesn't seem to truly have one definitive look. There's options here, but I do think my favorite is the green robed version Toybiz did do, but very poorly. I'd love to see that updated. I could roll with this older version too, but I DO have a gut feeling we'll just end up getting the rather bland suited version:
2. Comic Mephisto: He's another that's likely been avoided due to possible controversy, I mean he's in essence Satan. But boy do I pray we get him someday.
3. Comic Toad: It really is wild to think we got him all the way back in the very first wave of Legends. He's loooooong overdue for a re-make. I mean realistically, he was dated even back when originally released.
4 . Classic Comic Zemo: I'd personally go with the Helmut Zemo personally in his very classic look. We've still yet to get him, despite getting him in the smaller scale.
5. The Owl: Daredevil doesn't have a ton of big villains, the big have pretty much all been done. But if I had to pick one I'd love to see, most def. The Owl comes to mind. I always kind of viewed him as Marvel's Penguin.
6. Attuma: I sincerely hope we get this guy someday. He's pretty unique looking and while a little obscure, I would love him just to have a Namor villain.
BAF - The Executioner: This has to easily be the Thor villain that's MOST in need. I still can't believe we haven't gotten him.
And since 8 figures was an option, I'll do two honorable mentions:
7. Annihilus: I say instead of a BAF, re-do him as a deluxe figure. Think what was done for Archangel. I think a fully classic new version is a must eventually.
8. Baron Mordo: It would be awfully cool to get a comic version.
I'd be thrilled with these, but truth is...while these are my immediate choices, I'd be thrilled with classic Strucker, classic Titanium Man and Crimson Dynamo, Count Nefaria, Classic Blastaar, Wizard, Avalanche, Madame Hydra, Madame Masque, Man-Ape, and plenty more.