Teams bandwith in an VDI environment

We offered a Microsoft Azure Stack HCI solution as a talking point to a customer with with 9 branches.
They want (now with thin clients) with +/- 70 CCU via RDS to use office 365, sharepoint, an application in which building materials can be viewed in 3d and Teams
Teams in particular has caused quite a few problems in the testing process because all teams run session through the RDS hosts and thus have to share the bandwidth, and that performs to cry.
That is why it is thought to switch to FAT Customers to run teams locally with local bandwidth.

Now the end user has also stated that they stand for VDI, and that is all possible according to Microsoft, but I expect that this will require a lot more computing power and that men will have the same challenge that all teams will have to share the bandwidth of the hosts session.
If you then switch to FAT customers in order to solve the team problem, VDI does not have many advantages anymore, I think. Alle suggestions and help is appreciated.

So the questions are,

- should we suggest to them to stay with thin clients or change to fat clients. 
- what can we do to improve their thinclient / TEAMS experience?