Sliiiiding in on T65 with Settler first --> Great Lighthouse as inquired. Delay due to triple workboats and 5 warriors for fogbusting.
I poked around with it a bit, and it's possible to get down to ~T60 by having the second city send its first workboat back to the capital. But this leads to some weird gimmicky stuff:
1. Cutting back on earlier workboat commerce.
2. Ignoring warrior production in time to block barbarian invasion (T35 absolute on Diety --> using this as a safe measure)
3. Not having enough population in Prague to both work ocean commerce and produce warriors in time
4; Aachen grows too fast --> Settler whip into GLH is a real play but there's not enough warriors to claim adequate defense for a 3rd city.
I like full Settler first. I think my half Settler --> work boat --> size 2 --> Settler doesn't really make sense. With the spot I settled, it's immediately commerce neutral, something I had ignored.
Tech path: Fishing, Mining, Sailing, Bronze Working, Masonry, Iron Working
Approximate build path:
T17: Settler out, workboat started on 3 hammer
T20: Prague settled, begins workboat on 3 hammer
T25: Aachen workboat out, 12 turn worker started.
T28: Prague clams up, warrior production to size 2 --> finish warrior
T35: Prague warrior finishes, begins workboat for Aaachen. Warrior goes into jungle to buy time.
T37: Aachen --> worker finishes, begins lighthouse --> Great Lighthouse
T40: Prague is on fogbusting duty (5 hammers + ocean commerce duty) with a worker timed a little after Bronze Working for chopping.
T61: Iron Working in --> only 6 turns after my other date.
T64: Aachen just only grows to size 6, which is a perfect size for a 2 pop whip to build 2 Settlers to maximize GLH . 5 warriors and a scout out and about.
No 3rd city megapolis planning because of the GLH, but I'm invested in this currency bulb. Maybe this is the path to grabbing Monarchy + Great Library in time.