Selecting Army/Fabbers/Factories

I'm wondering if Control and Alt should force the selection of Fabbers and Factories.
It would make it easier to select crucial units among the haystack, and/or filter through the chaos of a large base, and it would also mean you can always select combat units by default.

Alt isn't even used for selection and Control is a toggle selection that isn't always predictable, so the loss is debatable.

Though, there isn't much leave room for a few other things I'd like to do:
Filter the selection for orbital units. Without completely disabling terrestrial selection.
Filter the selection for transports.
Filter the selection for loaded transports.

What say you? Have a better idea?