If Chinatsu/Akari, then Yui/Kyouko, Ayano/Chitose and only Chizuru is left out and she's not a main character. She could do threesomes with Ayano and Chitose.
If Ayano/Kyouko, sadly my favorite pair of all, then Chinatsu/Yui, but Akari has no one, Chitose has no one. Akari and Chitose could get together, or they could each get together with their sisters, or Akari could get together with Rise if she breaks off her teacher/student thing with Nana Nishigaki. Probaly Akari/Chitose would be the best pair-the-spares couple.
Another problem is that, honestly, Akari's best pair after Chinatsu is definitely Sakurako, probably the person that is the most respectful to her in the whole series. In that case you'd pair Himawari with Chitose.
The student council and amusement club don't have to divide themselves into 4 perfect lesbian couples. If you're feeling bad that there is an odd girl out and you have to forcibly pair her with the minor characters, you don't have to! Love can be found at any time, any place. Akari loves everyone anyway; she's never going to be ready for a relationship!
That being said, sorry Ayano x Kyouko shippers, but this pairing is the mismatch here. it's the reason why the eight girls don't pair up together nicely without loose ends, it's why there are odd girls out, unless you want to SEPARATE Himawari and Sakurako, or you happen to avidly support Akari x Chitose (which to be fair, the case could be made, but it's very weak). No offense to Ayano x Kyouko supporters, but they're just the Ayano fanclub, and it takes two to tango. There's simply no chemistry between the two; if Ayano were to have a crush on Sakurako instead, with her acting all tsundere to her and Chitose producing cute yuri delusions of them together, then the end result is the same, only this time they are Ayano x Sakurako shippers now. What I mean is that Kyouko really has done nothing notable to hold up this ship, Ayano is doing all the heavylifting.
Speaking of which, Chitose is essentially the typical Ayano x Kyouko shipper in character form, as she also supports Ayano's romantic endeavors! But deep down, she tragically locks her deep feelings for her friend with fantasies of Ayano's crush becoming realized, because she wants her happy first and foremost. You can see a very solid hint of her true feelings in Volume 13, Chapter 91. While Ayano x Kyouko indeed has the most material by a longshot, don't be fooled: it doesn't mean that they are the OTP! Majority of those juicy moments are Chitose's fantasies after all, they're not "canon" in the romantic sense.
Besides, how can you not see the appeal of role reversal childhood friends?!?! Kyouko x Yui for life!!! Though this doujin really gives that pairing a cruel twist.