I'm not sure why you think the Alliance would have no power in 2025, even with a simple majority needed for changes. Now, if the Big 10 drops out, yes, I would agree with you, but 3 of the top 4 conferences would offset the sway of the SEC and some of the Group of 5 are already against the proposed playoff as well.
I agree that the ACC would be 3rd in the revenue hierarchy even with ND brought into play. However, with ND, the ACC will at least be able to negotiate a deal near the SEC and Big 10. Without ND, the ACC will fall further and further away as far as revenues are concerned. Even if ND isn't a top 10 contender going forward, they are a national brand and bring in TV viewers. I hate that school as much as everybody else, but they have had their own TV deal for 30 years now, even through the Bob Davie and Ty Willingham years. So, not sure how you don't think ND would add much, but everyone has an opinion.
At the end of the day, I'm just giving my opinion as to how to strengthen the ACC's position (and therefore Miami's) as much as possible. If you just blindly allow the proposed playoff to pass, I think it would lead toward the further reduction of the ACC's power and revenue, which has already been on a steady downturn over the past couple of years.