Being an MT for only one mission doesn't quite cover the MT experience to become a Raven adequately enough.
Take AC3. There was an MT partner you could choose whom I believe was called Rogue. It was a red Bipedal Medium MT. You can choose her, or others, like Apple Boy, who was in a different type of MT. After a while, they become AC pilots. When Rogue became an AC pilot, she sent you an e-mail stating such and you could pair with her, now in an AC.
Point is, you didn't just pair with her once in an MT. She had to work her way up. I think that there should be an Armored Core where you do the same to get that same feel. I thought up another name for the idea, too. Armored Core [Rising].
Oh, and I wanted to add this about Armored Core 3:
Like Armored Core and Armored Core 2, you are given a trial mission to see if you are talented enough to join the mercenary group dubbed Global Cortex. New features within Armored Core 3 include consorts (additional allies that can be obtained to assist you in a mission), detachable weapons (thereby lessening your total weight and increasing speed), and a new Core classification; Exceed Orbit (EO) which sacrifices the power of Overboost and allows you to deploy a built-in, autonomous weapon on your Core.
And, for classic players, if I remember correctly, the Global Cortex emblem is an unlockable emblem in the newer games.
And to clear the confusion (I hope), I was mostly responding to the part about a test and the coordinators saying something about having potential. But I can't find AC3 right now. I think that most of the AC games have some sort of "test" for the first mission, to serve as a tutorial. Also, AC4 and AC4A have tutorials all to themselves.