While you might not be able to seem them in a sold jetway from the cockpit, you might want to use the Showcase camera or ( in MSFS 2024 ) the Avatar mode to see passengers, so we don't remove them.
In addition to that, while we might have a (rough) idea if a jetway is transparent or not if you were at a default airport where you used GSX replacement jetways, we don't have such information on 3rd party airports, since there's no way to know the jetway "style" programmatically so, at the very least, it should be a scenery customization option to be included in the profile, requiring to specify for each gate if the jetway is transparent or solid.