I think they could finish at the summit if they really wanted to, given that they were able to finish up Puy du Dome. A MTF from Ax les thermes wouldn't be great as it would have to be preceded by a large amount of valley roads.Pailhères can be used as a MTF if climbed from Ax-les-Thermes and with the finish ~700 m from the top. The road is very narrow on the other side of the climb only from the Mijanès ski station to the top (last 6 km).
I'm not bothered about a Pailhères MTF anyway, the Pailhères/Ax 3 Domaines works fine.