That sounds very good. For the use cases where you may want to mix CDK and Pulumi or migrate from CDK to Pulumi, relying on the bootstrap being in place should not be an issue probably.
It would be nice to not have a dependency to the CDK CLI to set up the bootstrap, but not a show-stopper.
Is it required to have Node.js pre-installed (to run JSII/Typescript), or is that bundled somehow?