Feature: Less random player roles

[alenros]

Currently the player roles are chosen randomly, with nothing being carried over between rounds.
Some players might prefer that since they play over a number of rounds, players who were not the Insider will get a higher chance to get the role.
An addition to this would be that a the chance to become a Insider will increase the more rounds have passed since he last was Insider .
This will add meta thinking for the game, which is OK.

A good solution would be easy for the players to understand.
I found this issue tricky, so if someone wants to give this a go I suggest we discuss it here.