There were extensive discussions in this forum about invading non-base/dot hexes and eventually the developers became involved in those discussions. You can search for them to see the whole thing, but the bottom line is basically:
- Of course players can have any HR they choose.
- The developers specifically looked at the issue of such invasions before release and did not/do not consider them to be a problem. Reasons?
- - There are penalties for such landings, as noted in posts above.
- - Terrain that is truly impassable to such invasions has been made so on the game map. That is, certain types of terrain do not allow unloading, appropriate hex sides have been made impassable, etc.
- - Various sections of terrain that popular lore has as impassable were even looked at in detail during the forum discussion using tools such as Google Earth and seen to have many, many passable areas not so different from the beach exits at Normandy. The difference, of course, is that Normandy was heavily defended whereas the landing areas we are discussing are undefended.
All that being said, I repeat that players are free to HR as they wish/reach agreement. The developers confirmed that the game (AE) does take into account the possibility of such landings and there are appropriate limitations (as noted above).
IMO many people harken back to their experience with the issue in WITP, which they might have found less than satisfying. The developers have confirmed that things are different now. I feel certain that a player will only contemplate making such landings for very, very special cases as the price is high. It is still up to the individual players, of course.
Even with no HR against such landings and two players who are each game to use them, I predict the odds of seeing even one in any given game to be less than 50%. That's my guess.