It would be really helpful to be able to able import a solution that contains a canvas app with SQL Server or some other connections. Right now, one has to import an unmanaged solution and then manually go in to the app and add the connections from the target environment. I have attached the error you get if you try to import such solution. If you have a managed solution, there is no way to fix that error.
It would be nice if it worked like importing a package where it asks you to connect your resources during your solution import.
Currently, with this limitation, one cannot sell/distribute their solutions with such apps because it requires the solution to be unmanaged as you have to manually edit the app. This is bad because you do not want unmanaged solutions for production.