The current state of textport is that everything is in single color and there is no autocomplete. Lack of this simple/standard features makes working in textport unnecessarily hard. It almost feels like you are working with some weird subset of Python and not Python itself.
Because the interpreter/REPL can not be accessed from outside of the TouchDesigner (unless you are willing to hack the life out of it), using an external interpreter or REPL with these features is not possible. Because the main interpreter can not be replaced, it’s also not possible to use different interpreter/REPL with different capabilities. Also, I believe this is the result of textport’s current implementation, the interactive options like IPython / bpython can not be used under the textport (They quit/crash immediately.)
Matching the features from IDLE would be a great starting point.