@stof Based on your suggestion in #60885. I am just not sure if it's worth it though as we cannot easily change the type in AbstractTransportFactory without breaking backwards compatibility for child classes.

Can you also update AbstractTransportFactory? I agree either we decide the BC break won't have any impact (because we consider nobody is going to redeclare the prop in a child class, which might be fine) - or we'd better not do the change.

I guess I tend to rather not doing the change at all. Not so much because of someone redeclaring the property but about how the property is passed to concrete AbstractTransport implementations created by such a factory.

Ah, all transports would need the same change indeed.
Let's close then. If someone cares with a real-world use case we might reconsider.