Clothing for the Aubrac in early to mid-October

The altitude is above 1000m for most of that segment. You will want layers; it can be cold (frost) at night, yet be warm (shorts, depending on personal preference) in some afternoons. Autumn storms are not out of the question; you should anticipate at least two rainy days in your trip (maybe more). I recommend a quick-drying baselayer (merino wool or polyprop long underwear), quick-drying trousers, two long-sleeve shirts, one short-sleeve shirt, a lightweight fleece jumper (not down unless the water-repellent type), lightweight gloves, and a fleece hat. You will want good raingear (possibly rain pants). And since things will be cooler, clothes will not dry so quickly -- I would take extra underwear and socks. Since there will be fewer walkers, some lodgings may not be open, so calling in advance to make arrangements would be useful.

The "Pass of the 13 Winds" is well named. Plan on some cold winds. (edit...that is south of the Aubrac, in the Haute Languedoc, but similar)

The lodgings will have blankets; so you might get along ok with just a silk sleeping bag liner. But this is shoulder season, and there is no guarantee that the heat will be on. So a lightweight down quilt (or a summerweight bag) might be more comfortable.

Rain pants and gaiters yes!
Last spring, end of May , I needed my rainpants to put over my trousers to be warm enough, even if it did not rain.