Hi Rongzhong Li, first, congrats for the project, im a big fan from the begining.
Im web developer, and i made as hobby some Nodebots with the framework johnny-five controlling Arduino running JavaScript on a Raspberry Pi.
I want to ask you if you think if could be possible to use JavaScript to program Nybble.
Here, some examples to manage Servos: http://johnny-five.io/examples/#servo
Options 1 & 2 are great to send commands to Nybble by a webpage, for example.
As i supposed, the option 4 requires to re-code all your work.
But i think, the option 3 would be a good option.
Thanks for the answer!