We currently got kind of 2 Tiers of Wood right now (Due avalability)
TierI: Fir, Oak
Tier II: The Rest
My Suggestion:
Tier I: Fir, Oak (avaliable as it is)
Tier II: Sabicu, Mahogany, Caguairan (Avaliable at 3 - 5 Ports around the Map)
Tier IV: Live Oak, White Oak, Bermuda Cedar, Teak (Avaliable as it is)
This woud make the Tier II Woods more attractive. Currentlly you go Oak/Oak + Fir/Fir or you go rare wich will always be Teak/white + Live/white. With an easier second Tier, you woud see medium ships with mabye Caguarian/Sabicu etc.