The balance team (I don't speak for them) generally avoids adding new units where possible to keep FAF resemblant of base FA. There were only a few exceptions such as the T3 MAA and even those were controversial.
I understand you want it balanced for lower-rated players, but I think it is best to balance around how units are played at the top level. Lower rated players and even ones at my level really struggle with some basic concepts, so it is hard to say if it is due to it being harder to fight at a lower level, or just less experience in the matchup:
If an Aeon player plays 30 ladder games, and we say for the sake of argument that all factions are picked evenly, then he will gain experience against 'normal tank' factions 75% of the time. On the flip-side, a UEF player will face a 'range tank' faction (aeon) only 25% of the time. So when you're a new player with only 30 or so ladder games, it's quite often that an aeon player of the same skill level will have double the experience in a matchup. This is part of what I think contributes to new players having trouble against Aeon.