I picked up a long track on my last deck project to set all of my boards long and trim to install the trim board. worked marvelous. not worth the cost of the track but at least 17.5% better.
To do what your talking about i would go to my skill saw with edge guide before my track saw (is there an edge guide for the TS i haven't seen?). This is all well before i would think about pushing and pulling a 20' board through my table saw (even with feather board)(I work alone most of the time).
I assume this isn't a big box store item, but, if it were and they have a panel saw, that sounds like, by far, the best option. It would take a 1/10 of the time to rip a few 20footers through a panel saw with great results than it would any other method. And the guys that have clearance to touch the dangerous saw would usually rather cut stuff than tell people where the picture hangers are.
But my vote is the trusty mag77 with an edge guide on the grass.
On a side note, i didn't bring my table saw on a recent basement stairway door trim out, track saw will take care of it i thought. 1"x79" mixed grain fir door case. Well the stock was bowed and because the track saw cuts straight she ended up at 1 3/8" in the middle. Had to bring the table saw for one cut the next day. So the track is amazing at what it does, in real world application not always the right tool.
P.S. I'm going for the runoff sentence and () king in one post.