where are you getting this 30 foot gap from? What is your fascination with this number?
This isn’t the Death Star, there isn’t a magical 30 ft gap Achilles heel you keep referring to.
Blast doors can be hydraulic operated that come through the ground. Same way silo doors are generated.
Also a mountain is by logic above sea level. So building into a mountain is not underground.
It is quite possible to build and would operate on a similar concept as carrier concept and hyperloop concept. You would have a storage area where aircraft are kept behind in fortified chamber. Iran has a lot of experience building these chambers.
Then you have a taxi area that is located outside the fortified chamber where 3-4 fighter jets can taxi behind one another at a time. That taxi area connects to 3-4 550-700 meter parallel runaways. One blast door at the beginning of runway and one blast door at the exit of each runway.
Upon alert the doors of the blast doors of each runway open and the fighter jets move into their parallel lanes. Then Engines are ignited and they take off.
Each parallel lane would be only 1/2 a missile base lane in terms of width (see below).
As you can see 4 of these bases scattered strategically across Iran would TOTAL have minimum of 80 aircraft (air superiority fighters) to fly out plus another 40 future Iranian supersonic UAV bombers. (So that means 20 fighter jets and 10 UAVs per base).
Now these bases would be surrounded by Skyguard AAA, automated short range air defense and would also be inside a Bavar battalions “kill sphere”.
Furthermore, Iran has extensive GPS jamming technology thus any CM entering the area would be subject to EW. All US cruise missiles rely on GPS for precision guidance.
Lastly something you simply didn’t think of is strong alloy “nets” that can be raised in front of the entrances of the base. Any CM trying to attack the blast doors would be sliced into pieces and detonate early. The concept is similar to “cages” around tanks and APCs that aim to slice the warhead of an anti tank missile and force it to detonate prematurely.
These bases would be in CONJUNCTION with the the standard Air bases located across the country that would house Iran’s other 200+ aircraft. The goal here is to make sure at least 60-80 air superiority fighters survive the first few months of war so they can protect the AD rings and take stress off the AD network. The idea isn’t to SAVE every Iranian fighter jet nor is it to make Iran’s entire airforce in mountain. But merely 20-30% (assuming a 300 fleet force).