@Gargantua:
Making exceptions for territories would be ridiculous
Exactly my point, I’m glad you agree. Being able to Scramble over neighbouring Sea Zones, but NOT over Land terriories is a ridiculous exception.
It is not an exception. An island/island group is contained within a single sea zone as given by definition in the rules. It isn’t adjacent to it. Building an airbase implies building up the infrastructure to meet incoming threats before they reach the island. Without that, its inability to scramble is just like land. Otherwise one would have to use carrier to defend an island’s own home sea zone despite the presence of an airbase.
The answer given at the beginning makes sense: if you want to use fighters to defend a territory from air attack, you should station them there. Otherwise with what you propose the effective defensive zone of a land territory based fighter with air base would be ~4-6 times that of an island based fighter with air base. A single fighter unit (wing or whatever it represents) could defend 2/3 of the continental US, one coast, plus a large portion of Canada, and most of Mexico.
Furthermore, allowing scrambling over adjacent land territories (many enormous) would unnecessarily complicate attacks, stealing the initiative from the attacker–which is a fundamental aspect of attack, concentrating at a vulnerable point. A large group of fighters in one territory could be divied up to meet multiple attacks in other territories by the same opponent on the same turn.
What you suggest would seriously unbalance fighters/tac bombers, giving them super defense capability.