Honestly, this was more of a puppy ship. What I mean is it's one of those pairings that I don't have much reason to see happening (not that it will, of course: the manga's not about that), but my issue with pairing Bocchi up with anyone is that I feel she's too pure. Pure as in she is very innocent and gullible.
Don't really think Bocchi has too much competency when it comes with the idea of being in a romantic relationship. Hence I find Nako more as the big sister in the friendship.