Yes, in a map where your opponents are your neighbors you will find difficulty in rushing air, but we are talking about a 20x20 largely naval map here. This is not Desert Arena. What you are saying is that the map should be a different map entirely and all map design should cater to creating that small niche of maps where t3 air rush isn't possible. That kind of thinking brings worse results in terms of gameplay, than t3 air itself does. It is simply not possible to avoid t3 air unless you want a completely new map - and even then (in cases like hilly plateau and sands of ablicka) if one player is left alone for a couple of minutes (which is likely in a game where attacking is discouraged with reclaim, acus, defensive structures etc.) he will be able to end the game with t3 air.
Now I don't want to go all ad hominem on you, but since this has a lot to do with the perceived strength of a strategy I have to mention that we have quite a large gap in experience on the subject. You can of course argue forever about how t1 bombers will rain hell on the "air player", but it doesn't change the fact that in a real world situation a couple of stationary anti airs will do short work of them. Or you can argue that it's possible to go for t2 bomber all in, but in a real game the air guy will just scout it and make some inties to defend while preparing to go t3 and ending the game with it shortly afterwards.
If you want to create a certain kind of land/navy gameplay you will have to accept that t3 air rush will be a part of your map no matter what.
For the record, the airspot in Selkie is vulnerable to naval raiding. 1 mex by frigates, 3 more by destroyers (depends which kind), and most if not all by cruisers.