Got a bit of an oddball situation here. We have a full suspension tandem with 145mm QR rear spacing. Want to get a Rohloff, which is normally 135mm QR but rumour has it a 142mm x 12 bolt-through version is in the works. I don’t think the 142-145mm difference in width is enough to worry about (could probably use a couple of mm of spacers and/or asymmetry if necessary) but my dropouts are of course the standard rear QR type. Also, I need some way of handling the hub torque. I’m wondering if it might be reasonable to drill out the current dropouts to fit the fatter 12mm axle, and maybe even cut flats for the torque (I think that is how the OEM rohloff dropout works, though I’ve not seen it in the flesh). The current dropouts are huge aluminium things, there’s plenty of metal there.
If it all goes wrong, the back-up plan is a new rohloff-specific tandem anyway so the risk isn’t huge.
(As for why rohloff, we are sick of mud and chainsuck, we already have another rohloff tandem and it’s working well for us. But it’s a hardtail.)