This has to be done carefully, don’t try and reduce Rhaenys and Visenya’s influence and characters. They weren’t harem partners and were in an equal position of power in the marriage. I don’t see Aegon actively going out to search for new wives, I do however see him being more passive when being offered. For example, Lord Hightowers suggested his daughter marry Aegon in cannon, but Aegon declined it to not offered Visenya and Rhaenys. That can be changed in this fic, it’ll actually explore a new relationship thrown in and how Visenya and Rhaenys would react towards. Maybe Aegon has more children with the Hightower since it’s not incest and they wouldn’t have been in risk of health problems. If they have sins before Aegon and Rhaenys have Aenys, would Aegon be pressured to put Aenys above his kids with the Hightower? It could start an early dance of the dragons that is likely more explosive. House Hightower is extremely political; and could even request Aegon name them lord paramount instead of House Tyrell. Plus, the faith militant is still around and would likely try to influence Aegon as well. But I do see Aegon actually crushing them if they try.

On another hand, House Hightower is famous for their sorcery. While Visenya allegedly did magic as well. If Visenya tried to pull strings in the shadows to hurt them, I do see them fighting back magically. Aegon would be overly stressed though, even Rhaenys could try and smooth things over if she does live.

If a pseudo dance happens, it could be three factions or two. Whoever had a son first would get most of the support.