I agree with your conclusion, but not the reasoning. If the Bahamut Aeon were to summon itself, it would be calling on the same resources that are already in use, and this is not possible, like why you can't summon Valefor while fighting Ptera (sp? Isaaru's Valefore in any case). Similarly, if the soul manifestation (the ghost of the kid) were to summon, he's energies would immediately be put into becoming the aeon, thus the ghost would fade, which then removes anyforce pulling the aeon together, therefore the aeon would not appear. This would be why any aeon could not summon itself. I see nothing ruling out the summoning of other aeons however, and am at a loss to explain a mechanism what would prevent that, but I do believe it may be possible, see next point.
Leading on from my previous point, Aeons can use magic, which is pyrefly manipulation. Also, Jecht, an aeon under current definitions, was able to become a fayth. He became an aeon aeon. This implies that whatever force was summoning him made his hold on the world so pervasive and impermeable that he was real enough to become a fayth, so I do not see why he could also not summon. Certainly being composed entirely of pyreflies would not stop him, see Belgemine, the unsent summoner.
One would think that this event would be quite traumatic, right? Then why, if he is refering to this, would he sound amused, as if he was remembering good and fun times? Unless my memory is wrong, he sounded nostalgic and energetic when he recalled the few fiends that DZ had seen.