It may not be exactly what you are looking for, but you can group units by type, or if multiple units are selected, hit TAB to cycle through the different available units' abilities. Check out page 20 of the manual, 'Selecting Units and Movement of Units'.
There have been a couple comments recently that hunters are fast and have good firepower, so are well suited to taking over building sites. With the current balancing it doesn't seem unreasonable that the AI would at least start off with lots of hunters (though if just focusing on hunters throughout the fight is a good strategy, that would be a balancing issue).
