I don't know. Yes, character choices contributes to a line's longevity, but I don't think it was the main determinant in the Indy line. Sideshow gave us heavy hitters like Belloq, Toht, and Jones, Sr. I don't think any of those were mistakes (may have been a mistake giving us Belloq in a suit, but I don't think that would have made a huge difference). Mola Ram was very possibly cost prohibitive for Sideshow. I don't think Marion would have sold well, despite big fans wanting her, because she's just not all that interesting looking as a toy. And I'm not sure a Map Room Indy would have sold well, either, because he's not going to appeal to the less hardcore Jones fans out there.
Indy is an incredibly popular character and is going to sell if done right (every Sideshow Indy release had a flaw or drawback of some sort which held back his true selling potential, IMO), but I'm not sure the supporting cast has a great chance to succeed as collectibles, no matter what type of collectible you are referring to. I just don't think this license has that kind of appeal, so I don't think selection of this character over that one played the kind of role you are speaking of. Just my 2 cents.