[support] Show a different theme with multisite

Hi.

I discovered today the feature in the settings.php file, of overriding a configuration variable. I'm using it for having in "beta.example.net" exactly the same of the main site, "example.net", but with a different theme.

My question is: can this be a source of problems? It's a good idea?

I don't know very much about database access, but I'm concerned of if this can lead to problems in the database, for example, with Drupal IDs, sessions, cache, or whatever.

Maybe a solution is turn the "beta.example.net" secondary site to read only, but I can't find a way of doing this after doing some searches.

Thanks in advance.