Even a Delphia is not a bargain, let's forget about the Dragonflies - I agree with Pollux - they are almost as costly as a megayacht.
Your basic idea's af draft
and currents in Rhine & Rhone are in need of some correction.
The Rhine - for which you need a "patent" to cruise and the Rhone do not have currents exceeding 3-4 knots. Down Avignon, the Rhone gets broader, wider, and current
velocity is similar to that of a fast walking pedestrian. (Which is fast enough).
, a max draft of 1.40 will bring you almost everywhere. Even in Friesland, where they have the most shallow waters of the country.
My boat has a draft of 1.40 and I can come everywhere. The main point is not so much your draft but the capacity to bring the mast down. And that is another story all together.
Edit: for the French canals, a max draft of 1.30 mtr will be more than sufficient for the Canal Lateral/du Midi.
You can go to 1.60 - 1.70 for the remaining main canals.
The North canals are even more giving: there you may go as far as 1.80 mtr.