I'd like to see air supply too, but troops that are cut off from supply don't become instantly useless. The imposition of supply penalties happens gradually over 30 days. That's plenty of time for a quick-moving invasion to link up with paratroops.
Yes, I know about "supply cache" every unit carries with them. But air supply is the least important for paratroopers - army in general used them as well to great extent. Just because it is a PLAN for an offensive to link up with paratroopers, does not mean that it will happen - plans in war usually do not go as you originally thought.
And that is why we need air supply missions. I get it, new air and supply system makes it impossible to air supply a single province - but what about copy of current supply system, naval convoys, for air supply? Just like naval convoy would supply port-to-port and its efficiency depend on naval superiority in the region - we could have "air" convoys airport-to-airport who's efficiency would depend on air superiority. Just like subs do convoy raiding, so could interceptors. After all, it was possible to supply large portions of the army that way.
And it has gameplay value as well - you might not have naval superiority, but do have air one. That way you could supply your units for an extended periods of time instead of just 30 days, and enemy has to deal with it.
And, for instance, low infrastructure and far regions in let us say Africa - air supply could help a lot for a small force.
I do hope supply system gets a major rework because it is missing a lot. What we saw in WWW was way too much - supplying hundreds of divisions in eastern Siberia and Tibet from Berlin, over huge destroyed regions, with poor infrastructure overall, filled with partisans? Ain't gonna happen. Ever. Not even today something like that would be possible even remotely.
In general, supply system works (simulates) for European battlefield. Everything else, it breaks up. Of all the things in HoI4, supply system is the weakest link. Removing air supply is just another nail in the coffin of the system.
Oh, and btw, I think that 30 days is way to much, even if it dynamic system (penalties get worse over time of those 30 days). A division involved in fighting would be out of supply much faster than that. Out of the fight, depends on the division. But we should be able to drop a paratrooper unit and supply it through the air, just as was the case in all the previous games.
That is how Sea Lion worked for me - blow up RAF out of the sky, drop paratroopers to surround the ports with big coastal fort values, take them as fast as possible and hold the line until some heavy equipment could be brought in. And I needed air supply to do it. Not to mention supplying surrounded troops. Demyansk pocket held for almost 4 months due to air supply. There is just no way around it - you cannot simulate and abstract it like most other things in HoI4. You need at least some basic airport-to-airport supply mechanics if not general airdrop mechanics.
I understand how new system works so I thought airport-to-airport should be doable. The best option would be both airport-to-airport and airdrop, with airdrop having penalties and smaller supply value - but I it is too much to ask. I don't think that copying existing naval convoy to air system is too much to ask though. I hope something like that comes as soon as possible in one of the patches.