Although Teams currently does not allow the sort of control you are asking for and as far as I am aware, is not on the roadmap. You can at least have full monitoring of all Teams conversations through SENSO.CLOUD however, which monitors all Teams Chats even without the need to have the client installed. This has made a huge difference to allowing more flexibility to using Teams, especially with distance learning and other lock down issues.
We are now not reliant on Teachers monitoring chat within a Team as our Safe Guarding Team are able to see any issues including the use of pictures which are also analysed which has already been of great benefit to us.,
https://www.senso.cloud/safeguarding-microsoft-teams/