At a glance, the debugger user interface looks much nicer than gdb's terminal ui. How tightly coupled is the debugger interface to the emulator/debugger engine? How much work would it be to plug in a different debugger, say lldb or gdb, into the ui instead of blink?

I think the user experience of cli debuggers is generally somewhat dreadful when compared to their gui cousins -- they seem to display a much narrower view of what's going on. Could the big blinkenlights debugger view be useful outside of blink itself?

You can go other way around and use other TUIs for GDB:

* https://github.com/pwndbg/pwndbg * https://github.com/longld/peda * https://github.com/hugsy/gef