high end skill cap is subjective, for example so long after the plank update 100 h&n isn't exactly high.
Splash damage would make seens in the form of an explosive device or some special pillage ability givind the splash but at a reduced rate to the.
From a different standpoint devs if you want to limit the number of walls to 1 or 2-3 in the case of more powerful settlements then their strength should be buffed 3-5 times beyond what it already is.