Currently, there is no point in capturing aliens (aside from selling them) and there is no reason to hunt specific alien types (I have found Non-Combatants, Soldiers, Officers, Engineers, and some others). The game is still in development and the end game has not been worked out at all yet, so is there going to be a point in capturing multiple aliens of a type and hunting specific types?
One thought I had was that interrogating multiple aliens of a specific type could add a diminishing returns boost to research on a specific topic. Engineers could boost research into the captured alien technology, officers/leaders could boost research towards base and aircraft upgrades, etc.
The first alien should give a large boost, next couple would give roughly 1/3 of the first, then drop sharply until you hit the cap. Something like: (Assuming a 50% boost cap) 1st = 15%, 2nd 3rd and 4th = 5%, 5th to 9th = 2%, next 10 give 1%. This would provide a boost for capturing many aliens and interrogating them, but make you weigh how many you want to actually spend time to earn the boost for.
The time was spent to add several alien types to each race of alien so I assume there is a point to it in mind, just thought I would toss in my 2 cents