What will make your platform perfect solution is voice channel which I think is really missed. An option to use twilio voice number just like the use of twilio online chat api. Option to set IVR menu, queues, group calls, customer contact popup upon call, click to call, custom greeting, set hold music, simultaneously ringing or ring by order groups, call back, call transfer and more...
Sip phones integration so when customer calls the phone will ring and the customer details will pop up on agent screen, when click to call the call will be made via the sip phone .
Of course every call will be saved as conversation and the agent will be able to write private notes and the call record will be available there.
It’s a big project but I think that this is really missed in your system. You don’t offer any voice channel.
I will be really happy to hear what do you think about it.