customer: money is interested in experimenting with Impeller on iOS (pending development verification of visual correctness). It would probably be easier for them to run an experiment if they can do a runtime flag that does not require distributing different binaries.

I think that this is already possible if you update your embedding, so this might just be that we should update https://github.com/flutter/engine/blob/main/impeller/README.md#try-impeller-in-flutter with some instructions about how to do this for customers who want to do experiments based approaches to rolling this out.

Looking at https://github.com/flutter/engine/blob/main/shell/platform/darwin/ios/framework/Source/FlutterDartProject.mm it seems like it might be difficult for an application to arbitrarily modify settings short of just creating all the settings itself.

@chinmaygarde @zanderso fyi