I am giving the Usurpers and their captain the option (as an incentive to keep R'lyeh as planned) by offering the following 4 extra subtereraean lake provinces in these locations:
These 4 provinces would be: 202, 191, 80, and 83.
3 of them are forest, but since these are underground lakes, there's nothing saying there can't be forests or trees on top as well. They would be connected to the merc but not with corner lakes directly and would not be assigned a VP.
R'lyeh's cap can be connected to one of these (whichever is closest).
This placement and connection with R'lyehs cap offer many advantages to both the Usurpers and the merc and everyone in general:
1. It extends R'lyehs offensive capability and range as well as the utility of its aquatic only units.
2. It doubles the mercs sea neighbors thereby giving a needed resource boost to the merc cap. And also extends their operating range.
3. It enables R'lyeh to reach the strategically valuable corner lakes via an aquatic only route, eventually, but at the same time ensures that R'lyeh would need to go through the merc cap to do so (and pay a suitable toll(s)).
4. The placement is evenly spaced, halfway between the center and corners but allows enough room for all to navigate around them, particularly the AI.
Again, I will provide these as an incentive to stick with the Usurper nations as originally planned including R'lyeh.