I'm still confused on what Rhaegar's whole "deal" was. On one hand we have him being described as a studious individual that just read books all day. Then he started reading books on prophecy and started to train in swords and stuff. Yet on the other he is accused of kidnapping and rape. Yeah, I get that the whole rape thing is from the other perspective and I don't believe for a second he did it but it still seems out of character. The whole giving a rose to lyanna instead of his wife. By all accounts he was a smart dude and knew this would cause issues. And the whole running off with lyanna thing when he seemed to be devoted to learning how to rule. Maybe it all had to do with the prophecy he read?
Like maybe he did initially think Ageon was going to be the prince that was promised. Just lije what Dany say in the house of the Undying. Rhaegar must have read something like, "only the dragon can melt the coming cold" and assumed "hey, Dorne is the sun. If the dragon mates with the sun THAT'S two heat sources, let's see this coming cold withstand that."
But then he probably read more and figured maybe the dragon needs to mate with the cold to make an ice dragon and went after lyanna. He has to have had a plan. He's described as being such a badass I can't see him losing his head over trivial matters of the heart.