Very much doubt Lezignan could support a Championship and a French Elite side, it isn't that big.Wouldnt the logical step be to have the Lezignan first team in the NL1 and their reserves (with Cats and Toulouse) playing in the first division. I dont see how this would harm the first division too much.
I guess an Aude side with separate Lezignan, Limoux and Carcassonne feeding in would be better as it would only take about 1/3 of the players from each team, so would help even out the Elite too (although may also mean in the short term Pia win easily). Longer term a Vaucluse side could be done in the Championship based on Avignon and Carpentras. If the Elite standard were a little lower they could get the top Elite 2 sides in (Montpellier and Corbeil being the top ones but ideally a couple of others) and the rest of elite 2 could be merged with National 1 and split west/east to cut down on the large travelling there currently is.
I cannot support a Paris team for SL though, unless there are roots to it