Your right about certain players in the scheme (or schemes in my scenario) not playing an active campaign role.
Chewie seems to be there as perfect bait.
Jabba has a bounty on him so it makes sense that any unknown will be able to use him to get into palace (though you'd think he could afford some kind of security which is why I would have the mighty Boushh arrive at the calm scene the droids see in the current versions, having already gone through a security check).
You can also see Lando being Leia's means of getting Chewie out safely.
As a team they could get a revived Han out.
It's one plan that doesn't need Luke or the droids if it works (which it doesn't).
Remember Luke isn't cocky when he goes to Cloud City, he is desperate.
He can sense the pain Vader will inflict on his friends and willingly places himself needlessly (but he doesn't know that) in danger.
That is what Leia is doing in my set up.
Luke turning up makes sense as a rescue for the rescue.
What doesn't make sense are the droids.
Sure Artoo sneaks a weapon into the fortress but Luke's trusting that he will survive to get into a position where Artoo will launch the thing at him.
He is also chancing it that Jabba won't just junk the droids one of which back in ANH looked a bit beat up in the eyes of a Rebel technician and was the second choice purchase of a moisture farmer protesting poverty.
And as for Threepio maybe it WAS something he said.
At the very least we should have seen Artoo hotwire EV-9D9 and fix it so he and Threepio get ringside seats on the Sarlacc pit.
Maybe even see a previous translator droid deliberately damaged so that Threepio would be useful to Jabba.
It's certainly something worth thinking about because if Luke really did plan everything he has a Poker face that should keep Lando guessing.