On the other hand, this will make Vietnam difficult to conquer not only while attacking its cities but also after taking them
this is also historical... And adds yet another tactical decision - what is better, getting city defense bonus or unit defense bonus? Yet another layer of Vietnamese defenses. Personally I don't see the lack of synergy here
outside of purely abstract divagations.
You could say the same thing about Canadian trait! First part of it:
- when cavalry remains in city, increases happiness
Second part:
- when cavalry doesn't remain in city it can claim neutral land!
So you're basically saying that first part of the Canadian trait contradicts the second one. I see interesting tactical choice here - what is better, tile expansion or happiness boost? The same with mine Vietnamese trait.
ALSO, you basically say that GREEK trait contradicts itself!
City-State influence degrades at half and recovers at twice the normal rate. - Greece, diplomatic civ shouldn't lose influence in city states below zero
See? Yet nobody complains on that.
The same thing happens with Ethiopia (spam many cities to get steles or go tall and gain combat bonus?), Sweden (awesome Carolean invasion unit and peaceful ability!) and few high quality custom civs (among them - TPangolins awesome Canada and mounted units
). 'Contradiction' or interesting unique choice? I prefer second interpretation. Contradiction would be something like 'has bonus faith points from Nachos resource but needs 50% more faith points to generate great prophet'
Also, I don't like straightforward and boring 'let's make civilisation which has only bonuses towards science'
Obviously, everything depends on TPangolin's and Senshidendhi's verdicts