When I first start a character, I focus on a few things. Hmm, Science, Energy Weapons and Medicine. I think I'll stick with that! Once I get a high enough level, I start increasing some of my other stats a bit, put some barter here, repair there and a hint of survival here. However, when level cap comes around, I am an expert at so many things it can get ridiculous. Your "unique" character just kind of melts into a Courier Who Can DO Anything. I am not against having a high level cap, because I love blowing [censored] up and wreaking havoc, so long as my enemies can too. However, I think that skills should be able to go to 300 rather than stopping at 100. However, you could argue, a Courier with 300 gun skill would be ridiculously OP. However, for each 50 you cross over 100, it's effect starts to dilute. I don't know the exact formula, but if 1 gun skill equals 1 extra damage, having a guns of 150 would increase gun damage by .5, 200 would increase it by .25, 250 it would be .012 and 300 would be .06. You could argue, what is the point of that? There really isn't much point, but it would be helpful with Guns that require 100 Guns skill to use, but a stupid ability causes your gun skill to go down to 98. It would just mean that RP wise or something, your Courier just knows a lot about weaponry by having a Guns of 300. If you choose to become a "master" and have a Guns skill of 300, you are draining yourself of skill points that could be spread elsewhere.
I think something like this would be a nice addition to Fallout. I want to be a level 50 master of destruction, but I don't want to be a Lockpicking Scientist Doctor Who can Repair Explosives with Survival by creating Energy Weapons with Guns and Barter master of destruction.
TL;DR:Raise skill cap from 100 to 300, every 50 skill points its effectiveness dilutes. It's a skill dump so you don't become a Jack of All Trades Courier, which most become after hitting level cap.