I think that's mostly right. There may be some kind of blueprint for it, not sure.
I lived in San Marcos for several years, home of the Texas State Bobcats. At the time they were in the Southland, a battery conference with McNeese, Nicholls, Steven F. Austin, etc. While I was there they committed a lot of money to upgrading their stadium to seat enough to meet FBS requirements, and joined the Sunbelt. I don't know how it's going for them, and I don't know if FCS --> G5 is analogous to G5 --> P5.
If it is possible, that doesn't mean it's reasonable for a smaller school.
Still, as far as the playoffs are concerned, I don't think there is panacea that satisfies all valid opinions. I can only offer that I think mostly those teams don't belong anywhere near Ohio State, Alabama, etc. in the playoffs, and I'm okay with the current rules that get them there in an unlikely scenario.
FCS->FBS is completely different than G5->P5. Not even analogous.
You can invest the time, money, and resources and make yourself FBS from the FCS. Technically you need an sponsoring invitation from a conference (although Liberty apparently was granted a waiver to go independent). But if you look at the number of schools historically that have gone from FCS to FBS, apparently it's not THAT hard to come by that invitation.
To go G5 to P5, it requires an invitation first and foremost. And those don't really exist.
If you look since 2000, there are basically only two schools that can be said to have made the leap.
In 2005, Louisville jumped from CUSA to the Big East. This occurred when the Big East was raided by the ACC, losing Miami, BC, and VTech. So in a desperation move, the Big East picked up Louisville. They then got picked up by the ACC in 2014 the destruction of the Big East as a football conference.
In 2012, TCU jumped from the MWC to the Big 12. As mentioned, this again was a bit of a desperation add with the B12 losing MU/CU/UNL/A&M and them needing to keep numbers, but it was also a bit of a reconnection with their old SWC mates. So there was history there.
Interestingly, after the Big East had its reconfiguration, less then a decade later it ceased to be a football conference at all, and it was rapidly losing any cachet it had as a "power" conference. With the B12 now losing Texas/OU and appearing to add BYU/UCF/Cincy/UH, I think they will drop from P to G, if they aren't raided further.
Conference realignment has been about reshuffling power conference teams, NOT about adding G-conference teams.
That's why it's the glass ceiling.