I think it would help for adoption of using multiple source models on a single dashboard if the model selection was stored when moving from one page to the next if at all possible.
Currently it stays on the last selected dropdown for that individual dashboard but this means if an end user is testing changes, they have to remember and change the dropdown for each dashboard they look at, and then change it back when in production. The changing it back when in production is probably the bigger concern (at least it is for current client) so that test data isnt being reviewed instead of production data.
The current client feels it is safer to continue with two versions of the app for now.