A good film capacitor repaired in the manner described in post #20 would be no more likely to short in use in a loudspeaker crossover than if it were replaced with a brand new unit.
The chance of that 1000Vdc film capacitor shorting out in use in a loudspeaker crossover used at domestic levels is close enough to 0% that one needn't worry about it.
I've seen plenty of blown capacitors in speakers, but not of the type we have bothered to repair.
I like your idea of wraping thin wire around the stub. It would allow a good amount of solder to build up secureing a longer portion of the end of the lead to the stub. To take it a step further, wrapping thin solder around the end of the lead, such that it contacts the stub, might make the strongest repair.
The strongest repair would be using XRK971's suggestion: "Wrap some tape around the body to make a dam. Pour epoxy into the dam to extend the potting to provide strain relief."
That said, AllenB's suggestion of cable ties (or Gorilla tape) to secure the new wire back along the body of the capacitor is the approach I have used.
When I did it, I used cyanoacrylate to secure the capacitor and stranded wire as a lead.
I've also butt-jointed a new lead with solder, too.
I've also butt-jointed a new lead with solder, too.