The crux of the problem here is civil-military relations. We are having those of us that have an inconsistent wishlist that does not add up.
Civics changes are for example best during occupation of a new city as we heal troops, for example. Delaying the attack on Cologne till all catapults are up to front as well as Khans Gatebreakers in addition to time it with courthouse building is also good playing. Then taking sucessive cities for Compass is also good playing.
What we need to do now is to agree on a timeframe for conquering the entire continent, and how to do that in a smooth manner.
We have five top priorities as it stands for 50 turns:
Fight and win German War (10-10-10-10-0), that is 40 turns.
Prepare and fight/win Roman War (0-0-10-10-10)
Prepare Civics Changes (10-Merc/vass-10-10-10)
Build courthouses, banks, markets and grocers (50 turns total)
Build relevant wonders (HE, NE and a few others)
In sum, we want to fight two longer protracted wars as we build up our economy (which is why we have to move "slowly") over about 50 turns.
A War that would handle both Romans and Germans in 30 turns, would require Engineering (road movement) and HE and Vassalage). With a 50 turn horizon, I can do without Engineering. HE is required to allow more cities to build their four commercial buildings (Courthouse, Market, Bank, Grocer). HE also allows us to build 2-3 wonders as well, as we get a war-specialization city.