That would be awesome. It would be very nice to just be able to network activate it, then have one settings page at the network admin level. There you could set one URL at that would then work for all subdomains and/or mapped domains. Eg. maindomain.com/manage for the top level domain, but also subdomain1.maindomain.com/manage and mappeddomain1.com/manage would all work.
For my purposes, a network activate like that could just remove the setting for individual sub-sites. So it’s only set once at the network level. But I suppose if you wanted to get fancy, you could have a setting in that network admin that would enable individual settings for each site, in each site’s admin area.