I agree, that seems like a bug rather than intentional design. To keep with the spirit of the mod, in that naval melee units should not become obsolete with the tech that immediately comes after their prereqtech , ShipoftheLine should have one the following PrereqTech&ObsoleteTech sets: Navigation&Steam Power or Warships&Armor Plating. It is hard to decide which of them is the right one. If we go with the one that requires minimum changes to the mod as it stands now, I think Navigation&Steam Power set is better, it is also more consistent with the manual except Ironclad's prereqtech, which is Armor Plating in the manual but Steam Power in the mod. I think it would be best if we can have a list of bugs, both for us and the author, to help with bug hunting. Taking the manual as the reference, these are the ones that I've found&seen in the forum:
Missing entry in modinfo:
<UpdateDatabase>XML/GameInfo/Enlightenment_Policies.xml</UpdateDatabase>,
Incorrect building class in Buildings.xml and Enlightenment_Policies.xml
"BUILDINGCLASS_BASTION" should be "BUILDINGCLASS_EE_BASTION" ,
Incorrect entry in Enlightenment_Wonders.xml:
Smithsonian Institute: FreeBuildingThisCity should have the value "BUILDINGCLASS_EE_ACADEMY"
In Enlightenment_UnitUpdates.xml
UNIT_ENGLISH_SHIPOFTHELINE should not have <PrereqTech>null</PrereqTech> entry (very minor stuff, but still returns error in logs)
Prereq and Obsolete Techs for naval units:
In Enlightenment_Units.xml:
PrereqTech should be TECH_NAVIGATION for Ship of the Line and English First Rate,
In Enlightenment_UnitUpdates.xml
PrereqTech should be TECH_EE_WARSHIPS for Frigate
Missing/Incorrect texts:
In "TXT_KEY_UNIT_EE_SHIP_OF_THE_LINE_HELP" : melee instead of ranged
Also I've got a bit unrelated question for experienced EE players: Do you think it would be a good idea to merge Surveyor and Archaeologist units? The new "Surveyor" unit, can be upgraded from explorer (but for a very high gold cost), can enter rival territories and can carry out tasks of Archaeologist, but it would be a civilian unit (or combat with very low stats, depending on which one is better for AI) with combat withdrawal promotion, the chance of withdrawal would also be boosted by Navigation School policy in Exploration. Also it would have high maintenance cost and would be limited to, say, five active units per player to prevent spam. I think Surveyor unit is a bit redundant currently, and Archaeologist unit remains useful only for 20-30 turns, bringing them together can be interesting.