As for the tarmac variants, I'm not really sure these are an option? I tried walking along the D35 once, and a police car stopped and told me it was illegal! Unless I missed something (although even if you look on Google maps, there are very few roads in the region...)?
Well, "illegal" I doubt it, but one of the reasons why I remember the stretch between Lodève and Lunas with such fright is that there's a choice between a lengthy mountain detour and a rather busy stretch of tarmac -- this is what's "complicated" about that stretch. I did by that point have a great deal of personal experience walking on busy and yet overly narrow tarmac, so it didn't overly fluster me, but I was certainly happy upon getting past that patch and into Lunas !!
(FWIW I did take the trail for the first half of Lodève to Lunas, and only switched to the D35 mid-way -- and yes there are some rather beautiful views up there ; I can see now BTW that there's a trail variant up there on that side taking you into Lunas, but you would definitely need an app to not get lost up there !! But knowing what I know now, that's probably the route to Lunas I'd choose personally)
And as for more villages, I was thinking of the
far more viable tarmac variant between Lunas and Saint Gervais-sur-Mare, almost none of which even needs to follow the D35 if you really want to avoid it. You can follow the old D8, cross over a bridge to the D35 a little less than half way, then just cross over it and take a teensy tarmac road passing up through Saint-Xist (tiny hamlet), then down again almost all the way to La Tour-sur-Orb.
Some tiny tarmac up into the mountain from there, then either carry on with that 'til you're above Saint Étienne-Estréchoux and take a footpath into the village, or (as I did having no map app in 2005) follow an even tinier road through a valley to the main road leading to that village -- very little traffic there, and the tarmac out of Saint Étienne-Estréchoux winds pleasantly along a river valley 'til Saint Gervais-sur-Mare and back to the waymarked GR Camino.
The route is great between Montpellier and Lodève ; and again after Saint Gervais -- but it's complicated between Lodève and Saint Gervais, as it forces you to choose between several non-ideal options, the traditional route having been tarmac'd over and made into an overly busy main road.
You know, I do actually need to think about all this stuff myself, as it's on my return route this Camino if I can manage to get it done, so I'm going to have to confront these difficulties a second time ; just walking the other direction ...