Just use the mission system- you choose your own difficulty.
But it does not revolve around me choosing a difficulty, but the game offering value (in terms of PP merits, rewards, etc) to my effort.
If you - or generally speaking the pvp open only crowd - believe my time spent in solo is less important that their time spent faffing around in open (dealing with instance issues and other shenanigans) and you penalize me for doin PP in solo, then we have a problem.
solo today you can run at 100% in min/ max builds that artificially keep large powers going.
Even then, it's still a skill issue.
I mean, i can laser mine 250+ tons of tritium per hour, while a lot of players complain they can barely make 100t per hour.
They say mining is bad, i say it's a skill issue
Again, to whom do you tailor those pve activities in solo? If we take my own example above - do you tailor it for the 10 people that can mine 100t per hour or to the 1-2 that can mine 250?