Should trump be arrested, on the 20th, when he steps off of the plane. As so he doesn't leave the country?

If somebody has valid legal charge then now's the Time to get it ready because of trump leaves the country for a non-extraditional country it'll be far too late

depends on what they decide to do with him

Not necessary - - just show some video of him getting on the airplane, then let the Secret Service take him to Leavenworth KS instead of Florida. Or just disappear his dumb asss - - the Intelligence Community will render the final judgement.

No one ever says what crime they think he has committed that would result in arrest.

Arrested for what? Liberals have convinced themselves that massive crime has occurred. LOL.