Good questions, Anthony
Each TDG is going to design itself. This will be a time of great democratic experimentation.
As TDGs merge, they will develop new structures that fit their area, history, and experience. Other than some basic features, I really can't say how any TDG will look like.
And yes, there will be a time when the TDG does take over from the current institutions of electoral governance. The USA has a pretty good formula for effecting that change. Canada has an amending formula as well, but we have seldom used it.
Right now, that ain't gonna happen. But as the current discredits itself and the TDG has matured to be a viable replacement, the people will take the TDG more seriously.
All this is better explained in Chapter 6.