Systems
I think the appeal people have for Masks is the fact that in reading PBTA games there's this narrative appeal (which definitely exists) but it also carries with it a barrier to entry which is a learning curve (as all systems have).
So for me, your first question is what barrier to entry are players willing to pay to get in. I look at something like M&M or Champions as a VERY high barrier to entry. I look at something like Masks or Worlds in Peril as a medium barrier to Entry. Next, you have games like Supers! with a lower barrier (but still a mechanical system) and finally, your basic traits-based game with no barrier.
When dealing with an OC game, I think the traits-based game is tougher. The reason it works for features is that people know what Jean Grey does by and large. On OC game traits are a bit foggier.
So with that in mind. If I were looking at an OC game I would heavily suggest focusing on the low to mid barriers; being Masks or Supers! as the baseline.
Setting
One of the above-mentioned games, Worlds in Peril, is also a PbtA game but it gets less traction than Masks because it is based on Adult Team adventures, characters who are established. It also does a few of the mechanics differently. However, with that in mind, I mention this to state that there isn't a necessity to have things mutually exclusive in that regard. I would be curious to hear what people like and their reasons for it. I think the Teen Hero coming into things has the appeal for those players that can handle failure. Because that's the big deal with PbtA. You fail a lot. Even when you succeed there's a failure in that a lot of times.
FC vs OC
Yes, I know this thread is about an OC game but I did want to voice this thought. The reason I believe FCs and OCs don't exist on a game well together is that FCs crowd out the OCs so quickly and readily. Someone mentioned that there is always going to be some duplication happening, and that's certainly true. But the question I have is has anyone ever attempted to tell players If you want to play Superman that's fine, but you only get these two powers not all of them? Putting the 'Features' on the same level playing field as the OCs. Just a thought I'd float. Sorry if it derails.