Starcraft 2: Rally point for Queen

I am not able to test it right now, but shouldn't double-clicking on the building select all similar buildings, and then right clicking on the location you want to rally do exactly what you want?

Alternatively selecting each building you want to set the same rally point holding shift should, afterwards again right klicking to the location.

Alternatively, you could add additional buildings to a control group later. Select the first building, then ctrl+#. Then select the next building, and shift+#. You can use shift+# to add additional items to any control group.

Blizzard has meanwhile introduced an in-game hotkey editor that allows you to change all keys and even have several different hotkey profiles. It can be found in the options menu listed as 'Hotkeys'.

There are multiple templates to choose from such as for example grid and standard, which can be used as a starting point to personalize the hotkeys.