What would you say the consequences (immediate, as it’d be hard to say after a few decades with the butterfly effect) of Daemon winning the Blackfyre Rebellion? I imagine we’d see a shift in power balances, Lord Paramounts being removed or power to the lords who sided with the Blacks, but what else do you see changing?

That’s an interesting question. A couple impacts:

1. more social mobility within the nobility. With the Lannisters, Tullys, Martells, Arryns, Baratheons, and possibly Tyrells removed as Lord Paramount and replaced, there’s definitely a lot more room to grow if you’re a knight with some chops vs. a world in which the same families have ruled the Seven Kingdoms for thousands of years. On the other hand, this probably means a higher level of social disorder and violence as those below seek to rise
2. redefinition of the monarchy vis-a-vis the Great Houses. Now here’s a tricky one. On the one hand, a monarchy that’s removed most of the Great Houses probably has a lot more authority vis-a-vis its chief vassals than, say, Aegon V had. Feudal monarchies work when the king has lands to give away and when vassals fear losing their fiefs. On the other hand, if you give people the idea that the Iron Throne’s dynasty can be replaced, you might be facing future rebellions from other dynasties.
3. Dorne divided. Given that the Martells are likely to be really unhappy about being unseated, it’s quite possible that Dorne leaves the Seven Kingdoms soon after joining them…but not all of Dorne. Instead, I see Daemon recognizing the Yronwoods as Princes of Dorne in control of the Red Mountains, given that that’s their natural powerbase, the stony Dornish are the least Rhoynish to begin with, etc. This is not good for Dorne, because it means that the Yronwoods and the Wyls and eventually the Blackmonts and the Daynes will be raiding south instead of north.  
4. Inheritance laws changed. Given the standard need for post-conquest legitimization (hence Aegon II’s decrees after the Dance), I imagine Daemon would change the laws of inheritance. Raising all bastards to the level of true-born sons would probably be too radical, but I could see something along the lines of making it easier for bastards to be legitimated, and giving legitimated bastards equal legal status, and making it easier for fathers to write wills choosing their heirs rather than going by straight primogeniture.