It has been a while since I've ridden sewups, but I have also taken them on a few multi-day rides, as well as commuting on them. And patched a lot of them, usually in the evenings.

I do, in fact, carry a piece of sandpaper. It comes in my patch kit, although I do realize there is some debate of the efficacy of sandpaper vs the "cheese graters".

A lot will depend on what is most likely to leave a person stranded beside the road, or cause significant damage to one's bike if one tries to ride through it. So... tire related issues hit the top of the list. Thus, one should also carry the tools required to dig debris out of tires, remove the tires, and patch or replace tubes.

A broken chain would be frustrating. Rare... but stops one cold.

Derailleur stops... rare to adjust on the road, perhaps less with indexed derailleurs, but say, if one throws the chain into the spokes, then preventing it from recurring is vital. I've broken a few derailleur cables. I usually just limp home with the remaining gears, but there are people who force the bike into a certain gear using the derailleur stops.

Something like a loose bottle cage, I'll ignore until I get home (although I discovered aluminum rivnuts and loose cages don't mix

I have had load related issues, and have snagged rope or wire along the side of the road to tie a load down, or tie a broken backpack back together.

I've yanked a cleat out once. But, it was only 1/2 mile from home. Doing it 50 miles from home would be frustrating, but still the bike would be more or less ridable. I think when I yanked the cleat, I did, in fact, use the Swiss Army knife to release it from the pedal. It might have been safe enough locked in the the pedal, but I chose to pop it loose.

Anyway, I do typically carry a few tools with me, but a multi-Allen wrench is typically at the bottom of the list (although sometimes with me). And, several things such as a chain tool work just fine as loose tools. The Swiss Army knife gets used much more frequently than anything else in the kit.