My feelings go the other way. I feel like there has been an elevation of Quinn & Lily above SG status and screen time. Not MG obviously, but the paths have been prepared for the final steps. They're interaction is definitely more romantic than say Sarah or Cammie or even Rio. I think Rio is a chance, she thinks she loves Tremolo, but even playing Rio, it doesn't feel like Tremolo feels the same about her. Good friend, do anything to help her, but not wife material (just my gut feeling). Where with Quinn & Lily, I think there's mutual attraction/love and no aversion to taking the next step for either girl or Tremolo.
My guess would be those 2 would be top of the list to get endings. And the progression of pimp/drug dealer/stripper to girlfriend/wife/mother would also be a cool story to tell. But you know DPC, there'll be a spanner or two in the works.
The reason Lily doesn't want that type of relationship is because of her work. She needs the money to achieve her dreams. If she is in love with someone, then she she can't take her clothes off in front of other men. The guilt (or whatever) would stop her. Even if Tremolo says he's ok with it, Lily won't be able to show the goodies to others. Lily is freaking out right now, because she is falling in love with Tremolo and has no idea how that is going to work. (I do want to clarify, Lily is my #1, so I'm arguing from bias). There could be another reason, but not necessarily, this on it's own, is a valid enough reason.
I've turned down Zoey on every path (just not interested), so I may have missed something. But I haven't seen anything to indicate she's closer to MG status than Lily & Quinn.