Hi Michael,
I believe there is no benefit for us to do that. If we make that change then I think it will cause an error if the file is missing so we would need to ship that file in the mojoportal packages and then it would overwrite the existing file during upgrades which means people have to maintain customizations in 2 files instead of just one.
It seems better if you put your custom connection string in an external file but you edit the web.config after each upgrade to point to your file.
It would be nice if all the sections worked like the appSettings section but they don't. The appSettings section allows you to specify an external file but it also allows you to set default directly within web.config and it will cause no error if the user.config file does not exist, bu tif it does exist it will override settings from web.config.
Best,
Joe