Improved_RWG is a mod that essentially lets you double or over double the number of cities and towns that you can generate. In turn, this allows you to create many more points of interest, including those juicy T4 and T5 points. The effect is to essentially make the map much bigger.

This is a 12k map generated with the mod.

As you can see, the mod essentially allows you to double or over double the number of cities and towns you can generate, and as such, you get many, many more POIs, including those juicy T4 and T5 points.