I am not sure what these extra dust caps are for or what befell the poor bearing cage but it was like pandoras box in the bottom bracket shell of this Miele Uno LS. These were all lying in there.

One never knows what surprises will present themselves when opening up a cavity. Stuck posts or stems. Not round balls. Pitted races are really the pits. One never knows.

I have shown this bottom bracket treasure before but I do get a kick out of showing it, now and again...

I have encountered a bottom bracket where the spindle and cups were toast, was a bummer. I saved it as maybe one day I can figure out a way to retrofit sealed bearings into it.
Will need a lathe and some tooling.

The best surprise I ever got from an old bike was the bottom bracket. I bought an old beat up Fuji as an impulse buy for something like $20. I get it home and start to overhaul things a little bit and notice that the bottom bracket requires some special tool that I don't have. Turns out to be a Phil Wood.

Me too! I found a discarded Campania frame that, as it happens, was their top line offering, and so was specced with a Phil BB. If I had encountered the bike earlier in its life, I might have also snagged the Phil hubs with which it was specced, but no such luck. I am saving the Phil BB for a different build.

You may need a mighty good lathe and some tooling you don't really care about. Those BB axles are normally harder than a coffin nail!

I have a bunch of no-good axles and no-good cups and I have access to the lathes that could do it, and I still won't - readily available sealed BBs are going to be lighter, stronger, smoother, and more durable, plus you won't have to machine hardened steel.

It might not be that hard. I cut one in half with a hacksaw, not a particularly high-spec one, but it was hollow (picked that one so the sawing would be quicker).

And it might not be that difficult, I just took a 26.4 crown race to 27 on a mini-lathe with a carbide tool, it was hardened all the way through; no trouble.

But I agree, in most case off-the-shelf will be better in all those ways than what most hobbyists could do. If I had a crank for which axles were not readily available, like a Gnutti spline or the 3-degree SR, and an axle that was otherwise unusable, it'd be an option.

but I want it to LOOK like a Campagnolo bottom bracket. . Got to keep up appearances.

Oh, those are good reasons! Carry on.