Best way to stream base64 encoded string to a web client

I'm familiar with how to create Storage entries using the interpreter over the serial connection.

My problem is that with the Espruino CLI I can't seem to send other than the main script file going to .bootcde during the upload (this is done by the --config SAVE_ON_SEND=1 option).

I tried to do something like this:

./node_modules/.bin/espruino --board ESP8266_4MB -o test.js --ohex test.hex --storage html:./portal/dist/index.html --config SAVE_ON_SEND=1 ./firmware/dist/app.js

It's not possible to remove the --ohex option, and the test.js output clearly only contains the E.setBootCode part.

Even if it's the only way to do it, I can't find any instructions on how to flash this hex file to the ESP8266 (probably with the esptool.py). But I would rather not do that and use only the Espruino CLI if possible.

I think it's clear now why I'm thinking about bundling the assets to the main script file instead.

Also it's funny that even though I don't connect to any device during the above command, it mentions that I'm using an old firmware.

Espruino Command-line Tool 0.1.30
-----------------------------------

--ohex used - enabling MODULE_AS_FUNCTION
Explicit board JSON supplied: "ESP8266_4MB"
You have pre-1v96 firmware. Upload size is limited by available RAM
Writing output to test.js
Writing hex output to test.hex

Am I using an old Espruino dependency or the board definition triggers this and there's a new ESP8266 name available I'm not aware of?
Mod: yep, if I leave out the --board switch it doesn't print that.