Theoretically, they could bifurcate your progression, so you could gain unlimited unlocks via arcade/solo play, but those unlocks could not be taken into multiplayer. Complex and probably not worth it, but it would work. I tend to agree in theory that in a game focused on multiplayer competition, progress should come mostly from, well, multiplayer competition. But it gets sticky when you have both solo and multiplayer rolled into one game with the same progression system.
For me, I can take a mobile-style progression system, for mobile pricing, or a traditional progression system, for traditional pricing. What I choke on is mobile progression for traditional prices.