Your proposition goes directly against my intent with marshes, which is clearly implied in the post you are quoting.
Wow, what a thus far missed opportunity.There are already 3 varieties of the marsh feature in the mod. But only 1 is used.
Can you show it as part of an existing jungle? Like, replace the existing marsh variety with the new one in Congo?
On a first look, it may help to colour grade the trees a little to make them more drab or blue tinted. Also, how does it look with a bit more underbrush?

Speaking of catapults, catapults spawn in the southwestern corner of the flipzone in the main branch as well. Ive seen that happen for England multiple times, and once for Brazil and Argentina as well.
I mean, the catapult spawn happens in the current map as well.This branch is not meant to be playable. There is no reason to start any other civ than Egypt really.