As an SDSU fan, I was opposed to the DI move and thought that it was foolish. 23 years later, while some suggest that we've just seen a golden age of SDSU athletics, I think the reality is a little more mixed, even though I admit to being wrong about the move. Football has been wildly more successful at DI than at DII, because the institution and donors decided to start funding FB. BB, VB and the Olympic sports have all prospered at the conference level but realistically, the hopes for these teams go no further than winning a conference tournament. And while Frost (now FBT) Arena is one of the best Summit environments, attendance pales in comparison to DII days and the bedlam that was old Frost against even non-NCC foes like Northern State. Even as arguably the top mid-major women's basketball program, the woman are lucky to win one NCAA tournament game. Of course in 2003, no one envisioned what the portal and NIL would do to men's college basketball. Still, I doubt anyone would go back to DII/NCC days.
I think the big difference between moving from DII to DI vs moving from FCS to FBS is that for the the xDSUs and UxDs, and even some of the schools that stayed behind, those institutions looked more like their soon-to-be peers in the Summit/MVFC than they did the Morningsides, the Augies, or the Marys, etc. In retrospect, its easy to see that we would become the class of our conferences. But whereas our institutions look like the class of FCS institutions, we don't look like the class of FBS. Short of a reckless multi-billionaire throwing lavish money at an institution, there isn't a scenario where our institutions even sniff sustained competitiveness against the P4, let alone the P2. My hang-up with a potential move to FBS for SDSU would be taking the one sport where national championships are possible, and reducing it to a scenario like all the other sports, to wit: The conference championship game (if it still exists), is the pinnacle of that sport's success.
The only attraction I see to FBS is if there is a some kind of a split where the G6 has their own playoff but as noted earlier, G6 won't instigate this for fear of losing access to CFP. If it would become a reality, effectively creating a new second tier of CFB, that's where I'd want SDSU to be, and I think the AD has made it clear that that is where SDSU belongs. Unfortunately, I'm afraid that the admin feels like the window to move is closing, whether because of pending legislation or otherwise, and is feeling pressure from the NDSU move, and that we'll hear sooner, rather than later, that SDSU is ransoming their way into FBS as well. This belief is entirely uninformed but AD Sell plays things pretty close to the vest and it wouldn't surprise me one iota to learn that a lot of discussions are being held behind closed doors on just how to fund such a move and backchanneling to potential conferences.