The argument for a WVU or UCF in the ACC has to do with the future landscape of sports media. As I understand it:
ESPN pays the ACC a base fee of $240MM a year for the rights to the "top tier" games. This is their right of first choice of x many games per week to air on the national ESPNs and ABC. This is undervalued relative to other conferences's broadcast Network deals. The SEC's upcoming deal with Disney was reported to be 'mid-$300's' for fewer games, before the additions of UT and OK. The ACC agreed to that as part of the negotiation to entice Disney to partner on the 'linear' ACC Network. Which is where the real potential money is: the ACC schools get a percentage of the ACCN revenue. The B1G and SEC networks have an advantage of a head start and more time to have negotiated carriage deals (this is a big part of the payout discrepancy). They also started before the shift to cord-cutting and streaming really took off. The new ACC commissioner, Jim Phillips, has been publicly clear that getting the ACCN on more services is one of his top priorities. Comcast is the major cable provider in much of the ACC's geographic footprint and doesn't carry it. Getting that deal done will be a big boost to the ACCN's revenue. More eyeballs = more ad dollars. Getting the ACCN on more new-media streaming platforms will be important moving forward.
The only way to really renegotiate the $240MM base fee would be to add a school like ND that really ESPN wants. ND and the ACC could negotiate ESPN tough to bring ND into the GOR. Otherwise, they could sell the ND media rights to NBC, Youtube, some Chinese company that wants in on American media markets... There's not another school available that would really bring ESPN to the negotiating table.
For the ACCN, the ACC was late to the game and fighting the last war. Launching, just as streaming and a la carte programing become more the norm than big Cable packages. The ACC needs to think about what will drive revenue in 2025, not 2015. In the future, it's going to boil down to who's willing to pay $15/month for the add-on package that includes ACCN to whatever streaming service. Wake and Duke just don't have that many alumni or fans. WVU, UCF, aren't traditional powerhouses. They don't move the needle on whether Comcast feels like their subscribers are going to demand the ACCN or cut the cord. But they have big alumni bases and potential. Programs rise and fall. There's absolutely no reason UCF couldn't compete for (real) national championships in 10 years with P4 money for their program. WVU has been a competitive program at times. You can talk up academics and prestige all you want, but to quote Animal House: "We need the dues!"
Yes, WVU has a rabid fanbase, but not the hundreds of thousands UT or tOSU have. But, UT and tOSU aren't available for the ACC to add. It's a question of the best option(s) available.