I think if Greene was recruited with a torn ACL, then she must have something to give. She put up good numbers in the JUCO ranks, which is a significant step up from the HS ranks. If choosing between her and KK, I would expect her to have more of an impact as she's played an additional 2 years against tougher competition, plus her experience in the England National Team.
Middleton will be a senior and has put up good numbers this year, so I expect that she will be given priority over the freshmen as long as she is producing. I think Holly will initially have MeMe ahead of them in the rotation. She played a lot of minutes this year and she'll be an upperclassman. If Holly puts her behind the freshmen at the start of the season, she might as well transfer.
Harris has the potential to be a contributor...more so than Nia Moore. To clarify, she has a great body for basketball (get your mind out of the gutter!). She doesn't need to be a dominant post player or the centerpiece of the team, but after a year of being in the program, she should be ready to contribute backup minutes as a sophomore...potentially more than KK at the get-go.
Tennessee will potentially lose a lot after next season: Alexa, Jaime, and Diamond/MR if they don't leave this season. This incoming class is the #1 recruiting class, and they will have to live up to the hype. UConn lost the top 3 WNBA picks, and they are carried by underclassmen who were not key players for them last year. That is what the 2017 class will need to shoulder come 2018, and if they don't, then they just weren't that good to begin with.
Cooper, Hayes, Massengill, Jackson and Westbrook is a solid guard rotation. Davis, Collins, Greene, KK, and Harris is a good start in the frontcourt. 2018 recruiting is still underway, and the recruiting team is going after a few forwards and wings. If they get one of each, they will be in good shape for the 2018 season. They won't be a championship team, and maybe not even a FF team, but they have the pieces they need and if they pick up two more positional recruits in 2018, they will have depth at each position to handle injuries. If you expect them to have 13 McD AAs, with 8 of them patiently sitting on the bench waiting for some crumbs in case of an injury, I don't think that's a realistic expectation.