Here’s my take on the rescue plan. In order to “fix” the rescue plan I first wanted to understand what the plan actually WAS so that we could then remove any elements that contradict or work against it.

Plan A: The droids arrange for a meeting with Luke. Luke plans to negotiate/ use a Jedi mind trick to get Jabba to release everyone. Luke either gets the droids out as part of the deal or leaves them for Lando to smuggle out.

Outcome: Jabba rules this out immediately upon hearing Luke’s message. Lando presumably informs the team that Plan A has failed.

Plan B: Leia infiltrates Jabba’s court and attempts to break Han out. The haste of the plan means that she must sacrifice Chewbacca to buy credibility. If successful, this plan requires Lando to smuggle Chewie and the droids out later.

Outcome: Jabba doesn’t fall for the deception. Everyone is captured now except for Lando and Luke. Lando presumably informs Luke.

Luke arrives and makes one last attempt at Plan A. This fails, leaving…

Plan C: Everyone to fight their way out. Luke was likely hoping that Artoo would be present to provide his smuggled lightsaber but with Artoo absent Luke resorts to stealing a blaster. Whether he planned to kill or merely threaten Jabba is unknown.

Outcome: Everyone captured.

So what elements of the film do I feel work against this?

The need for the word “presumably” in my summaries speaks at least to the perception of the plans complexity. The audience is left to piece a lot of it together. In fact it wasn’t until I wrote it all down that it made some sort of sense.
The “Flanderization” of C-3PO. While Threepio is certainly a worrywart, that personality trait has become a caricature in ROTJ. In ANH, Threepio successfully bluffed past Stormtroopers on the Death Star and was decisive in choosing when to leave hiding and try to board the Falcon. In ROTJ the caricature version of Threepio has been left out of the plan and (because of his ignorance) could easily work against it at any moment.
Poor execution of the Boushh deception. Chewbacca is brought in with only a neck restraint, while in ANH they knew that binders was a better sell. Red flags were raised with Chewie overpowering Jabba’s guard in the stairwell but allowing Boushh to so easily tame him.
Luke’s overconfidence on the skiff in claiming that everything was under control when all plans had failed by this point.

Potential improvements:

Plan transitions: Would it help if we made the transition from Plan A to Plan B more obviously necessary? We’re limited to what we can do with what footage we have. One easy target would be through Jabba’s subtitles. E.g. Currently Jabba’s dialogue that puts an end to Plan A is as follows:

“There will be no bargain.
I will not give up my favorite decoration.
I like Captain Solo where he is.”

Perhaps it could be expanded as follows:

“There will be no bargain.
If this so-called Jedi shows his face, kill him.
I will not give up my favorite decoration.
I like Captain Solo where he is.”

Strengthen C-3PO: Start by strengthening Threepio’s character by removing obvious dialogue like “Oh look, its Captain Solo and he’s still frozen in carbonite” and “Oh no, Chewbacca”.

Next remove dialogue that shows him to be ignorant of the plan. Going one step further, can we incorporate him into the plan? A few people have already mentioned the brief scene after the Chewbacca exchange where Boushh is facing Threepio (just prior to the Boba Fett nod). Subtitled audio of Boushh could say something like:

“Stick to the Plan. Tonight.”

A few moments later we see Lando in disguise, so we know that something is afoot.

Selling Boushh: Instead of having Chewbacca shove the guard, would it be possible for him to be killed by blaster? Would it be possible to add additional chains to Chewbacca?

Luke’s overconfidence: Cut Luke’s line:

Just stick close to Chewie and Lando. I’ve taken care of everything.
As well as Han’s response.

Those are just my humble $0.02.