I don't want to buy a "weekly pass". But can I just purchase a Navigo Decouverte pass (5 euros) and reload it with a Daily choice at the kiosk? We're going to be arriving in Paris on a Friday. Like to do the "unlimited day" at 8,45 euros per day for four days (i.e.) Sat/Sun/Mon & Tue.
Yes you can purchase a Navigo Découverte card (€5) and load it with only day passes. You can also do the same with a Navigo Easy card which only costs €2. You can add up to two day passes onto a card simultaneously, and you have to choose which days they will be active (up to 6 days in advance).