The only way that I have found to "mix" avatars is to create a series of routes, using whichever avatar is appropriate for the specific leg.
Earlier this year my wife went on a cruise, flying from the UK to Croatia and then on the ship to various ports. I created one map for the flight and one for each day's "journey". The resulting video is thus divided into each day's "adventures" and ending with the overnight journey (travel map) to the next port.
In theory, if you want to create just one map covering the whole journey you might be able to do it as a series of individual maps which can then be placed, one after the other, on the PS Timeline.