Mock and Polyfill ZAFClient for local dev and Jest testing

Hello,

I'm trying to implement best practices with my ZAF sidebar app and bumping into some problems.

1. I'm using secrets that get injected by the ZAF Proxy
2. When compiling in dev mode for bug tracking my application is too big to upload to the Zendesk Sandbox to test
3. Uploading a compiled application for every minor change is an untenable development lifecycle
4. I need to be able to use Jest to run automated continuous integration testing on my app
5. Sinatra from Zendesk Apps Tools prompts for secrets but does not inject a working ZAFClient into local dev
6. ZCLI doesn't seem to have enough maturity to address these issues yet and is confusing to integrate into an app built using ZAT, React, Webpack and Zengarden.

I've left comments on the GitHub repositories also, I'm very happy to develop and implement something, but I'd like to understand how to get involved and contribute meaningfully.

The ideal outcome will provide the opportunity to mock a ZAFClient for local development, where I can mock the proxy using whatever code I need, taking full responsibility for the security of that on local dev.

WebPack would compile with the mock on dev/localhost, and a similar or different Mock using dummy data would apply to Jest testing. 

This will allow local development of the app, rather than 'guess testing' and trying to debug by beautifying compiled and minified code in the browser developer tools, which is clunky at best.