Basically not really viable. You'd have to do all or nothing.
Personally, I think if such a "all-out-war" scenario is happening. Ramstein airbase, and any US airbase in Europe used for resupply or take-off of heavy bombers are all up for grabs or French Naval base in Toulon and other areas that involve resupply and recon, I think their is a large recon base in the UK that receives SAT information. It would only be a logical thing to do from Iran's perspective and all of it is very possible and can even be prepared today with the current technology available. Hence I've always thought most threats to be bullshit, since only diplomacy is the only option. Frankly, the IRGC has humbled West Europe. Such a conflict would be a surprise for many.
It is not like Iran is escalating anyways, in a all-out-war, they will try to level every piece of infrastructure in Iran that has military or duel-purpose use, setting the country back 40 years or so. They will use thousands of long range missile till they run out of stock. They will not spare any building or collateral damage, so why return these luxuries to them.