“Isn’t great” is selling it short. Maekar exiled himself from court because Bloodraven got picked as Hand. Listen to any time that Egg opens his mouth about Bloodraven, and you hear his father’s hatred and the hatred of the people in his father’ party:
“His Grace should have made my father Hand. He’s his brother , and the finest battle commander in the realm since Uncle Baelor died. Lord Bloodraven’s not even a real lord, that’s just some stupid courtesy . He’s a sorcerer, and baseborn besides.”
“The old High Septon told my father that king’s laws are one thing, and the laws of the gods another,“ the boy said stubbornly. “Trueborn children are made in a marriage bed and blessed by the Father and the Mother, but bastards are born of lust and weakness, he said. King Aegon decreed that his bastards were not bastards, but he could not change their nature. The High Septon said all bastards are born to betrayal … Daemon Blackfyre, Bittersteel, even Bloodraven. Lord Rivers was more cunning than the other two, he said, but in the end he would prove himself a traitor, too. The High Septon counseled my father never to put any trust in him, nor in any other bastards, great or small.”
That’s not just Stannis being mad at Renly over Storm’s End. Maekar thinks that Bloodraven is a false lord, that he’s a sorcerer, and the people around Maekar are saying Bloodraven is a traitor to the crown.
Their mutual antagonism is so clear that even lowly hedge knights know that “Aerys is weak, and when he dies, it will be bloody war between Lord Rivers and Prince Maekar for the crown, the Hand against the heir.“ And at the end of Mystery Knight, it looks like Bloodraven agrees, because he basically tries to take Egg as a hostage against Maekar: ”I have half a mind to take you back to King’s Landing with us…and keep you at court as my… guest.“
Going from this point to Bloodraven as Maekar’s Hand is a complete 180 degree shift. I’m not saying that it’s impossible, but that everything we’ve seen in Dunk & Egg to date is moving in the opposite direction – which from a writerly perspective is GRRM making the task of bringing them together more difficult for himself.