All right, I understand your points on centrism and the current political system. I also think that there needs to make changes on how politics are conducted. In USA there is still a mainly two party system.
I find Sanders as a very honest and ideologically driven person. A much better alternative than comparing to Hillary Clinton and Trump, Personally I favor ending war on drugs and decreasing military spending, as well as decentralization.
When it comes to freedom, I do not agree that Sanders is a freedom oriented person in the first place. In Europe he would equal to a socialist or a left-wing populist, meaning that one is usually very collectivist or authoritarian in economic questions.
For example, since he has Sweden, Denmark, or Norway as inspiration for welfare it means that he supports high-tax welfare state system that have more than 100 different programs, large bureaucratic systems and also lot of control and commanding behaviors towards the individual. Also, when it comes to immigration Sanders is more of a protectionist and collectivist rather than promoting ideas of free immigration.
An interesting thing is that northern Europe as Sweden and Finland are much more deregulated and open economies than the USA. So if Sanders is for freedom he could promote ideas as basic income, state and local rights regarding humanitarian immigration, visa liberalization with Mexico and green-tax reforms (so that green taxes lead to reduction of income taxes)