Agent_047
I was pretty sure you were going to add aliens to the story eventually, but I thought it would be after he ruled over earth openly or at least in secret through reprogramming the leaders by offering upgrades in body and mind like he does with his soldiers and employees. As long as you don't give the aliens FTL drives so distance still matters, this will give Aron a deadline and the motivation to improve that he would otherwise lack since he has conquered more than enough space and power for himself and his loved ones. Without a threat, he could focus only on eden/esparia, making them the #1 power on earth easily before the story caught up to today, but with the threat of alien invasion, he will be forced to reveal and spread his tech widely depending on how close they are and how fast they travel.