ESP8266 support - alternatives?

I subscribed to the maker plan in the expectation of full ESP8266 support even on a chromebook. This is what the info in the help center seemed to indicate. I was already using the Web IDE on ChromeOS for Arduino UNO development before and I love it.

Now that I learned that I could have spent that money better, I still don't want to give up just yet. So here are my questions:

1) When I do 'verify and save' I can see in the browser network console that it will upload the ESP8266 binary to the browser. Is there a way to download that? I could at least use that output for a manual OTA upload to the ESP8266.

2) Is there a way to use a local build server instead, maybe on a raspberry that would then upload the sketch to the ESP8266 module?

3) Is there a way to use the arduino-create-agent running on a remote PC to do the upload?

4) Is there a documented API to the chrome app that I could use to build a custom uploader?

Greetings, Wolfram