Distance is the main issue. They could only do it if they took about three or four stages through Spain to head across the north from San Sebastián across Euskadi, Cantabria and Asturias to get there. The only way I see it being possible is if the Tour started near there and then had a big transfer back to France, which I see as unlikely because a) ASO wouldn't want to stick a climb like Angliru out in the first three stages and kill off a lot of intrigue from the word go, and b) Asturias isn't one of the richest parts of Spain and seems more than happy with bringing the Vuelta in instead.
Now the sentiment, if it regards wanting the Tour to incorporate some climbs that are steep enough to ensure time gaps and prevent the trains from being able to control, then sure, but Angliru is not really a realistic option for that. Also remember that the Tour has bigger space requirements than the Vuelta, so the in-the-middle-of-nowhere finish types like at Los Machucos or Ancáres are not as feasible for Le Tour. There are some climbs the Tour doesn't use that mightn't be Angliru-like, but are plenty steep and have ski stations that could be interested in hosting the race, such as Plateau des Saix and Super-Collet, which hosted the Dauphiné in 2011. If they are happy with their descents, there's the Iparraldean monsters like Ahusquy, Errozate, Arnostéguy, and you could always go from Soudet to Bostmendieta and either Bagargui (which could host a finish) or Larrau like in my fantasy Vuelta stage
here.
And if it's about the Tour using some Spanish climbs, then fine, as long as they are reasonably located that it doesn't require logistical headaches to get there. That limits us to the French-bordering regions of País Vasco, Navarra, Aragón and Catalunya. However, that does mean that for the most part, those brutally inconsistent climbs are off-limits save for the Basque ones. Perhaps San Miguel de Áralar, like in the 2014 Vuelta, would be feasible, but otherwise you'll be limited to the likes of Port-Ainé, Cerler, VallTer2000, and so on.