Run it like they do at the ski resorts. That seems to be a proven mechanism as almost all resorts have a similar fare structure, including to some extent timberline for the Magic Mile Chair.

For regular users/commuters using the tram would pay a slight premium for their annual/monthly/book tickets that give full systemwide access including the tram. Don't penalize those who wouldn't use it. Ski resorts with trams work this way.

7 day passes can be priced with an unlimited option use during the 7 days or with a lower cost one time use round trip option. The 1st for visiting business people who would use it for commute purposes and the 2nd for tourists who intend to use the tram once. One day passes can be priced similarly.

And then for the sightseer a one time ticket with TRAM access would be $4 which should also allow for system wide access to the rest of the mass transit system for the normal 2hr time window and or day pass of similar configuration.

My concern with opening up the tram to all tri-met riders at existing tri-met fares is that it may overload the tram and prevent or limit its intended use. If the ridership is at capacity a priority set of rules need to be enforced. This is also done at ski resorts. Intended users get priority over the sightseers