Have to say, I did really enjoy getting the Aggressor suits early on. My first campaign as well, so I have no idea of the various niches of the higher level armors, but it might be fun to have a "codex-flavored" (and restricted to that codex) higher level armor. Of course, that may already exist, I just may not have found/seen them yet.
Working around the limitations of the Scorpion hasn't been too bad, I've never been one to hide in the ship on the first turn, so getting out and clear quickly is nice. And with some of the enemy spawning right at hand I can usually take them out fast, which is a nice jump on each mission. And I've now built my Metallo, so I have larger transport capacity when needed. All of the undersea missions have had low enemy counts, so the Snake has been sufficient (bought a Blowfish for a while but got rid of it for a second Snake).