Look at Vito's background. His family is killed by a Mafia don. He loses his job to Don Fanucci's nephew. He becomes powerful through murder and earns "respect" by protecting the disenfranchised in his neighborhood. His whole life is defined by violence, fear and power.

I think what he wants is for Michael and his descendants to not live in that environment. To have the ability to change things to the point where they can pull the strings so that the Don Fanuccis and Don Ciccis of the world are put out of business.

In short, I think Vito was a criminal (or deluded himself into justifying his crimes) because he had no other way to get ahead.

I don't think Vito meant for Senator Corleone or Governor Corleone to explicitly assist in the Family's criminal activities but rather to get the pezzonovante out of the way so people can live their lives and run their businesses without interference, fear or violence.