These are all way to control the Med without a Navy. I have a Navy, I want to control the Seas.You can't control where your allies put their fleets. Typically the best way to get involved in the African theater as Germany is to position a few divisions in Libya before the war starts so you don't risk them being sunk in naval transport after the war begins. You can use these divisions to take control of the Suez Canal and push into the middle east later, or whatever else suits your purpose. If you want tanks in Africa but need them for Poland and France in the meantime, you can just convert the divisions you sent down there into tank divisions when you need them, and convert your European tanks into infantry so the equipment goes to the African divisions.
The easiest way to take Gibraltar as Germany is to invade Spain and go from there.
I want to take Gibraltar, then get Naval dominance in the Med and after that take out north Africa, Egypt and Syria (and Malta and Cyprus and Corsica).
The plan is to set up a naval invasion from Marseille to Gibraltar and try to get naval superiority with few Subs, Naval Bombing and distraction. Maybe they pull a fleet out of of the Med if I convoy raid with a surface fleet at the coast of Portugal....