Shield Emitter Blocks: The solution for "Gigantism" and fighters.

[Malacodor]

I feel like this idea would create some serious balance issues, and the games performance would also suffer from having to calculate what counts as an exterior.

It wouldn't even be possible. Just make a one block opening somewhere and suddenly the inside counts as outside. Then you only had to hope that no upstart jedi happens to pass by and fires a lucky missile through the hole.