Ian can have serious and loyal relationships with Alison, Holly and Lena if you so choose. Possibly also with Cherry and Cindy, though this is currently up in the air.
Cindy certainly feels like she can be a serious and loyals relationship... caveat being she's obviously cheating on Wade while in a relationship with Ian.
I would say Cherry is a serious and loyal relationship option, it just isn't as developed as some of the other girls at the moment. Hopefully that is set up to change with the recent developments with her before going to the MMA tournament.
Honestly I really like Cherry, and I'm a little disappointed how infrequently she is used, and generally how she is used, example being walking home with Axel or going over to Ian and Perry's to... reveal a little about Lena's backstory rather than being her own character. Like she's just there really. But then we have scenes like the art gala / afterparty and in her apartment with Ian where I feel she's an incredibly interesting character that I'd like to explore more of.