There will be a small section of a few songs they will do acoustic (SOS) each night. In that small section, 2 will be changed on a nightly basis. Welcome back to the 2015 e stage.
I'm not sure you can rotate one song unless you add it on some nights or drop one song some nights without replacing it. I'm thinking it'll be a bit like e+i where we got Gloria some nights and SOBL others, i.e. one in; one out.
I'd say for the first few nights we could see a couple of songs getting rotated or replaced as certain songs might not work in this new configuration that they are doing for the first time and then with a new Drummer they may feel he's better suited to playing certain types of songs .
With substitute drummer it will be probably none or 1 maximum. Maybe if they play some acoustic section (without drums), they could do 1-2 more (like last song on Popmart shows)
If the substitute drummer has to learn 22 songs, I’m pretty confident he can learn another 2 more for rotation purposes. There’s often been a rest point or acoustic section for Larry and Adam mother take a break so that’s possible.