It's been a while since I've read fAegon theories, so I hope this wasn't a point that's been discussed to the moon and back.
There is a point that kind of sticks out with me when it comes to Aegon that Varys peddles- if he really is the child Elia and Rhaegar had, why wasn't he transported to Dorne and raised there, under the watchful eyes of his mothers family, rather than shipped off to some godforsaken part of Essos on a crappy little barge with very little security, and I don't mean security against any assassins- I mean basic security like not coming across pirates or sailing around Stone Men? Yes, it would be dangerous for Dorne to be harbouring a Targ heir, but he didn't have to be presented as such, we've seen how Ned successfully pulled the wool over everyone's eyes for years, taking Jon and passing him off as his bastard. And that was honourable Ned freaking Stark, a guy who was hardly known for being a ladies man the way his best mate was. Who do we know that had a beloved sister that was dead before her time and at the same time known for being sexually promiscuous and known for having bastards? Oberyn! I'm sure that if it came to sheltering his sisters son by presenting him as his own bastard and then raising him in relative comfort and level of education offered to his "half-sisters" and cousins, he would've jumped at the chance, or left him with Doran the way Robert left Edric Storm with Renly. That way the perfect little Targ heir is raised by his uncle as his dad, and Martells have someone to rally behind when they get a chance. Aegon wouldn't even have to suffer the same problems Jon had, Dorne is far more accepting of bastards, and Sand Snakes are fairly well treated (too well, given their insolence tbh). Now, there is a problem with his potentials Valyrian looks, but purple eyes are not unheard of in Dorne- Daynes are known to have those, and in any case, Dorne is sufficiently close to Essos to explain any Valyrian features in Oberyns offspring- and he is known as a man who likes his variety in women, so he could just say he got him with some Lyseni gal he met at a tavern. He is different from Ned in that he's rash and known to be dangerously cocky and impulsive, but I'm pretty sure he'd understand how much danger his nephew is in if he shoots his mouth off- and there is Doran, the more cautious guy who would give him support.
The only few reasons they wouldn't leave him at Dorne is a)security and potential danger to Martells that Doran wouldn't want to chance b ) Varys wouldn't want to give up an important chess piece to other players, and c) the kid has nothing to do with Elia and he wouldn't want to risk Martells finding that out. The first two can be worked around- Varys and Illyrio were ready to commit Vicerys to Martells and Doran was happy to play the convoluted game of trying to bring him and Adrianne together (in which case they should've sent volatile Vicerys somewhere safer than Dothraki plains, where he could meet Arianne in secret, which any Free city qualifies for), and Vicerys is no less important in terms of Targaryen succession than Aegon - in any case, Martells would be more likely to fight for their blood than the unstable son of an unstable father. And the last bit could also be worked around, because Martells wouldn't suspect anything even if the child looked nothing like them or their sister - people don't normally look beyond obvious marks such as eye/hair colour and any prominent mannerisms and features- they could look at any generic Valyrian looking kid and see their sisters only son because it's what they'd want to see.
I hope this not completely off the topic, as this is about doubts to fAegon identity. It's been a while since I've discussed fAegon theories so I apologise if my idea isn't new.