@Timeshift: Interesting theory!
I agree that the lighthouse town is some sort of port and that the scaffolding is evidence of a relatively industrial area. There's a good chance that it might be a Steel-type gym!
I thought I might bring up some information from 2ch that details N, the alleged Elite 4, and the Champion:
2ch said:
・N(エヌ)=ノウス (プラズマ団団長) - N = North (Leader of Team Plasma)
四天王 - Elite Four
・ファラ (ノーマル、ひこう) - Fara (Normal, Flying)
・シュテン (かくとう、はがね) - Shuten (Fighting, Steel)
・カゲハ (ゴースト、あく) - Kageha (Ghost, Dark)
・ムロウ (ドラゴン) - Murou (Dragon)
チャンピオン - Champion
・サウス (Nの兄。使用ポケモンは混合) - South (N's Brother. Uses a mix of Pokémon)
In other words, assuming that this is accurate, that leaves the following types available for gym leaders:
Grass
Fire
Water
Rock
Electric
Bug
Ice
Psychic
Poison
Ground
From what we've postulated so far, there are four types left over: Poison, Ground, Psychic, and Bug. We know of a Bug-type gym (see below) existing somewhere, probably in the forest north of the eastern mountains.
For argument's sake, let's say that the Ground-type gym exists in the town undergoing construction (see below), probably east or south of the eastern mountains.
Let's assume that the lighthouse town doesn't have a Gym, that Hiun has a pollution problem--it
is a huge city, after all--and that there's a Psychic-type gym somewhere on the east of the map:
1) Sanyou - Dento/Red Hair/Blue Hair (Grass/Fire/Water)
2) Shippou - Aloe (Rock)
3) Hiun - ? (Poison)
4) Raimon - ? (Electric)
5) Sekka - ? (Ice)
6) (Northeastern forest) - ? (Bug)
7) (Eastern sandbar) - ? (Ground)
8) (South of eastern mountains) - ? (Psychic)
A lot of speculation, and it revolves around the 2ch rumor being accurate, but it's something to consider nonetheless.