[edited] if you have problems with hooking up the WebIDE over TCP/IP, you could introduce a serial to TCP/IP proxy? There are some suggestions for doing this in the second section of http://blog.philippklaus.de/2011/08/make-rs232-serial-devices-accessible-via-ethernet/ Nice idea to remote program the Pico
@Moray started
Espruino is a JavaScript interpreter for low-power Microcontrollers. This site is both a support community for Espruino and a place to share what you are working on.
[edited] if you have problems with hooking up the WebIDE over TCP/IP, you could introduce a serial to TCP/IP proxy? There are some suggestions for doing this in the second section of http://blog.philippklaus.de/2011/08/make-rs232-serial-devices-accessible-via-ethernet/
Nice idea to remote program the Pico