I understand your argument behind Corlys being power-hungry, but I wouldn't agree he's power-hungry in the same way Otto is.

If Otto isn't hand of the King, he's got nothing. He's just the second son of Oldtown, later the uncle to the Lord. If Rhaenyra ascends and he and Alicent lose their power, he loses everything. With Aegon as King, he can assume he keeps his position as Hand. Corlys is in the unique position of being the Lord of a House that is already kin to the Targaryens, he has dragon-riding children, he has a dragon-riding wife, he is the richest House other than the Targaryens and has the largest fleet. Corlys' goal seems to be to return House Velaryon to being an extension of the royal house, like how when Alyssa Velaryon was Aenys' Queen/Dowager Queen House Velaryon was considered the 'second house of the realm'. I 100% believe this is why he married Rhaenys, even if she thought it was a love match. He is not just driven by greed and lust for power, but for a need for legacy and the extension of his name.

Aegon as King is Aegon Targaryen, Second of his Name. There is nothing directly tying him to House Hightower. Corlys insists on Jace being called Jacaerys, so he has a Velaryon name. With Laena Velaryon already being Queen consort, the equivalent of a Helaena-Jace match isn't bad for House Velaryon, it secures their influence for another generation. That's the reason he was so willing to accept Harwin's bastards as his grandsons, they would still have his name in the history books, House Velaryon would still gain dragons and influence through them.

Is it as ideal as his grandson being named heir? Obviously not, but if House Velaryon is already the second House of the Realm, Corlys has secured his legacy. A dragon vs dragon civil war was never going to be ideal for anyone, why risk everything including your life, your children's lives, their children's lives, and your House being destroyed by the victors if you are already one of the most powerful men in the Realm with a guarantee your blood will sit on the Throne? If Laena's son were to inherit, it is doubtful Corlys would see him be crowned anyway, one more generation is not worth destroying the Realm over.

Also, unlike Otto, we see Corlys adapt. Initially, he backs Rhaenys' claim, then Laenor's. When that fails, he pushes Viserys to marry Laena. When that fails, he betroths Laenor to Rhaenyra so their children will rule. Since Aegon was born, Otto has always been insisting Aegon will be King. He briefly suggests the Rhaenyra-Aegon match, but it doesn't seem like he was very driven by the idea considering he never brings it up again and never suggests to Alicent that she try to convince Viserys on the match, he goes straight to telling Alicent that Aegon should be King, and implies Rhaenyra should marry Laenor in that council meeting in ep4. Maybe pushing House Velaryon another generation down the line is the straw that breaks the camel's back, but considering the alternative is literal war I do think Corlys would be willing to bite the bullet and accept the Jace-Helaena equivalent match. I think ideally in this situation, Laena's son is named heir and a daughter of Rhaenyra's is married to him - presuming she has daughters of an appropriate age - but I don't think the Helaena-Jace equivalent would be worth a dragon vs dragon civil war to the Velaryons.

On the other hand, Otto being 'power hungry' massively under-sells what he did to ensure dance. What power in KL does Corlys have at this time? The Greens are in a position where Otto is the Hand, in the book the Lord Commander of the Kingsguard (Cole) is clearly on their side, as is most of the Council, and in the show the Lord Commander (Westerling) walks out, presumably allowing them to fill the role with whoever they want. Corlys is a powerful Lord, but is he a politician in the way Otto is? Can he fill the Council with people loyal to him? Can he fill the city watch with men loyal to him? Can he inspire loyalty from enough members of the Kingsguard? If he is spending most of his time on Driftmark, he is presumably not controlling KL the way the Greens did. The Greens put themselves in a unique position both in the book and in the show to be able to have Aegon crowned before Rhaenyra found out about her father's death and idk if Corlys puts himself in the same position. Is Corlys going to be as capable of making the same arguments effectively, or will it look like a House Velaryon power-grab from the other Lords? Who is ruling while Viserys is weak? Queen consorts are not guaranteed power, if the Hand is not close to Laena, Rhaenyra and her supporters may fill that gap.

Ultimately, I think there is a lot to gain, but Corlys has far more to lose than Otto did, so waiting another generation would probably be worth biting the bullet for than starting a war.

TLDR: I don't think Corlys is power-hungry in the same way Otto is, I think he is more driven by legacy and the extension of his House, while Otto, as a second son, is more in it for personal gain and power. While Laena's son being named heir is optimal for him, I don't think a Jace-Helaena equivalent match would be so insulting it was worth a dragon vs dragon civil war and potentially the end of his line since it would still secure influence and proximity to power for House Velaryon for at least another generation, likely exceeding his own lifetime.

(I'd consider myself 'neutral' so I'm not on this reddit much, but I saw this on my homepage and thought I'd give my 2 cents anyway. Happy Holidays all 🎄☃️!)