I was actually thinking about this the other week when the presale thread was in flames and someone said something that more or less amounted to "I'm a bigger fan than most others, I deserve to get multiple tickets for half a dozen gigs. Unworthy casual fan (who'd be happy to see U2 just
once) be damned."
I'm MASSIVELY paraphrasing there, obviously, but I do think any U2 fan club gigs would just end in complete chaos. You can't please everyone.
If they DID do a bunch of fan club only concerts, I personally think they'd need to go down the very successful road Glastonbury (among others) has, having photos on the tickets and a unique number you have to enter for each person when booking. It probably won't happen as live nation would lose a lot of that juicy resale cash but still..
And they should limit the number of tickets to literally ONE pair per person for the entire run. But you'd obviously have a few entitled cry babies saying they've been screwed over by being prevented from getting rail four nights in a row. But at least it gives everyone a fair shake!
Then, more importantly for most of us, there's the setlist.
I think most of us, not unfairly, read "Mostly Rarities" when we see the words Fan Club Gig. But there's no perfect balance with a band that's nearly 40 years old and, again, you can't please everyone.
And even if they did decide to go down that road, that's a couple of dozen songs to re-learn, work out a live arrangement for in some cases, make a setlist that works well with them etc, chucking in Streets and (of course) One.
Considering they can snap their fingers and watch an arena sell out instantly (until recently, at least) to see them play the hits, that's probably a shitload of work they may not feel they need to bother doing or, if they did, wouldn't exactly take on a LONG tour, which brings you back to the ticket scrum!!