I’ve played in big bands for over 50 years. I’ve gone through every phase of thinking about this, from “there’s no way I can play that piece of ##” to straight reading. Ultimately I think this: read it as is until you are thoroughly familiar with the chart. If the chart doesn’t have changes, borrow the guitar chart or piano chart and pencil them in. Once you know the chart and you’ve heard it played, you might take some liberties with the shape of a line if it really doesn’t lie well on the bass. Don’t mess with the rhythmic content. And if you’re seeing the chart for the first time at a gig, read it. If you’re subbing in for another player, read it as is. In that situation no one wants to notice how great you are - they don’t want to notice you at all.