An eight team playoff would require seven games. Why can't these seven games be labeled as bowl games such as Rose Bowl, Orange Bowl, etc. and played in large destination stadiums?
If the teams are good and their fans travel then they can play anywhere, especially if the playoffs drag on and most people would rather spend it in California or Florida than Oregon.
The same consideration goes for all the northern tier schools. Football is a rugged game meant to be played under all conditions. (I have gone soft and will make an exception for serious lightning and Category 5 hurricanes.) I do not think Miami, Florida State, Alabama, and USC should get to play for national championships pretty much at home year after year. I'd balance a playoff geographically, and if that means playing on Jaunuary 1 in Lincoln, Nebraska, or South Bend, or Ann Arbor, or the Meadowlands on a rotating basis, that's fine. Let the southern teams make the adjustment for once. The players can switch to sissy indoor football when they move up to the pros.
But seriously: let's take the idea of college sports and sportsmanship seriously. Flip a coin, and play the playoff games at the winner's home field, with tickets split 50/50.