Bottom brackets that have plastic retainers have a reputation for being problematic to remove. Often the tool interface on the plastic retaining ring will shear off if the plastic is old or the bottom bracket is stuck (How can I remove the stripped plastic cups of a bottom bracket?). I (everyone?) would like to avoid such a situation if possible.
What steps can one take to improve ones chances of sucessfully removing the plastic retaining rings?
The plastic rings are typically made from Polyamide, which is resistant to attack by hydrocarbon lubricants. A penetrating oil might work (to the extent that they work anyway).
The plastic rings are made from a thermoplastic so heating is probably a bad idea. Having said that, it should be possible to heat up the bottom bracket shell with a heat gun or similar to around 100 Celcius. This would expand the bottom bracket shell by some fraction and make it easier to remove the retaining ring. Unfortunately the coefficient of thermal expansion of the rings is likely higher than that of steel. Maybe freeze the rings instead?
Maybe it's possible to attach a metal fastener (by pinning perhaps?) to the retaining rings. I expect this is in the realm of fantasy.
EDIT: To clarify, I am asking exclusively about threaded bottom brackets.