We colored each station, depending of which line go through them. So, we have to enlarge some 'square' for have all color displayed (and so, deleted one station Raspail [RSP])
Each line is now represented by a railroad. For keep a good readability, the background was turned to black.
Each 'Porte' is prefixed by a minus P, each rail station is prefixed by a minus g. We still search another way to distinguish them between the others stations. Maybe an outline, or the name in bold black.
About the river stuff. I'm agree it's underground, and so, La Seine can't be seen. But without it, we just have a black disc, which means nothing. Keeping the river path allow us to recognize Paris : Paris is often (even always) stylized by a schematic oval shape crossed by a reverse 'U', even for an underground map. It also allow reader to see where is the north, and where is the south, depending of the U direction. That's why we keep it.
About the RER lines, they don't have enough stations in inner Paris and/or just copy another underground line :
RER A copies line 1
RER B & D have only 3 stations
RER E has 2 stations
Only RER C would be different, with its 3 ways line, but not enough to have it : it also weighs down the map
We also look at the T3 Tramway but its position (each Porte from pSV to pVI) disturbs the Porte bonus and gameplay.
About the idea of a central objective, it may be having all 5 rail stations during one turn. In this condition, we may not have a standard bonus for holding them, but an auto-deploy bonus. with 5 starting neutral on each, except gCH : 10 starting neutrals