I wonder if in the future we might expect overhauls to include a silicon balance spring upgrade. And perhaps other parts. Or an option for that. I wonder if that would be feasible.
Very unlikely, at least in the near term. The only movement that it would be feasible on would be an older 8500.
I would assume that the impulse force provided provided by the pallet fork to the roller jewel is not the same between a steel hairspring movement & a silicon hairspring movement (but I could be wrong). Just wouldn't hold out a lot of hope for the ability to mix & match parts among unlike movements, silicon material or otherwise.
I've read how brittle these springs are when manufacturing the movement. Is it a real hassle for you watchmakers to take them out, clean them and put them back in when overhauling?
The combination of balance and spring still has to resonate at the same frequency. So you would get some of the benefits of a silicon hairspring by swapping out the assembly, like the amagnetic properties. I'm not sure (I don't know) whether silicon hairsprings have lower losses, but without a change in the mainspring (longer and weaker) you wouldn't be able to take advantage of that.