I agree that there were attempts to get a reunion up and running in 2006-ish, but I'm not sure how involved Axl was; it seems pretty clear that Azoff was actively trying to make it happen, but Axl saw it as an attempt to undermine the CD band. The moment wasn't right, not least because he was trying to get CD out the door, and a reunion would mean spiking the album and reworking it with Slash and Duff, just as Axl thought he'd got it pretty much locked down.

I think it's more that you can get away with billing Slash + Axl as a reunion, but ideally you need one more person there to reach a critical mass of mainstream acceptance. Axl + Slash + Tommy + Izzy + Frank etc would be just as acceptable to the casual fans who consider the NITL line-up a "reunion".

Duff was always more likely, though, partly because he's the business-minded one so he was likely the one who engineered the reunion in the first place (I've never bought that story that he "just happened" to bump into Axl in a hotel). Also because he and Slash have worked together consistently in the past on Velvet Revolver. There's also the fact that there's historical precedent for Axl + Slash + Duff + some other musicians as "classic GN'R" because even during the band's heyday, that was the UYI line-up.

I never really thought they'd get Matt back. In Velvet Revolver they needed him for the aforementioned "critical mass" - Duff + Slash is vaguely interesting on its own, but Duff + Slash + Matt is suddenly a "GN'R reunion minus Axl". But just from his book you can see that there's a bit of a culture clash between Matt and the others.

It just made sense to plug Slash and Duff into the already-tested touring machine that was Axl's GN'R; Axl wanted some of "his guys" there to balance things out, the Frank/Fortus rhythm section already knows the songs, they're not going to rock the boat etc.

And once you have the Big Three, you've got that critical mass you need to call it a "reunion," so Izzy, Matt, Gilby and Adler are no longer needed. Hence you offer them guest spots at a fixed rate.  It's harsh, but it's good business sense.

I think Frank comes in for way too much stick; he's a perfectly decent drummer, I just personally rate Brain over him. And Frank knows the songs inside out, he'd been part of the touring machine for years when Slash and Duff came into the fold. A much more reliable prospect than either Adler, who could flake out at any moment, or Sorum, who by all accounts sounds a bit of an abrasive personality (the fact that he published a story about Duff supposedly bad-mouthing his colleague, behind his back, tells you all you need to know). Frank was the obvious choice.

NGL, though, the NITL band with Brain would be the ultimate modern GN'R line-up.

Didn't Axl have piano lessons when he was a kid? I'm pretty sure he'd know what a bar was by 1993, he'd been a professional musician for years at that point. Loops, yeah, I can believe he wouldn't be familiar with them 'cos that's more of a production thing.