Happy to modify and have a go at the Web IDE if you can suggest right approach...
For the ESP32
env.CONSOLE is coming through as
setSlowWrite(true) is called in
versionChecker.js. In this case
SERIAL_THROTTLE_SEND has no effect. I think the options are either to provide an explicit block size for slow sends only, which is what I've done or provide an explicit block size for all sends slow or not.
@Wilberforce, Gordon says that flow control "can be enabled". Do you think this is a possible option for ESP32? In which case we wouldn't need hacky options.