More I think about it, Boston has 2 options here...
First will be to tether themselves to Kyrie and move out most of the picks and young players for Davis. I think this is what Kyrie wants (and will demand in return for staying) and this is what Ainge wants. Most likely Tatum, Rozier and others will not be here next season leaving a vet heavy team in Kyrie, AD, Al, Smart and Hayward.
This might improve chemistry, but I have my doubts Brad Stevens can coach this kind of team.
Second is not resigning Kyrie, letting Mook walk, resigning Rozier and using the picks to get even younger. Horford opts in. This would give you a young team where the youth is the majority. Only Al, Hayward and Smart would be older guys. Tatum and Brown would be the focal points. Plus you could have 3 first round picks. This would be where Stevens would excel. Young team like college.