Stage 4: Enter Luke Skywalker
From the get go, Luke Skywalker's entrance into proceedings undermines every other character in this so called plan. By walking straight into Jabba's palace, using the force on the guards and Jedi mind tricking Bib Fortuna into letting him in to see Jabba, Luke pretty much shows us everyone else in this scheme was pointless. If Luke could get in to the palace this easily it begs the question why everyone else even needed to be there (and placed in danger because of it). From there on in it all goes downhill. Luke is playing with his new found Jedi attitude well and rather than trashing the place and saving his friends he plays it calm looking for a peaceful resolution to all this. Of course he still pulls his blaster out to shoot his way out of the situation before being dropped into the Rancor pit to face the next hurdle in this quickly collapsing plan.
Why Is Luke Actually There?: There's a couple of ways to answer this question. Luke either had to speed up his own plan of peaceful negoation after Leia's plan with Chewie didn't work, or everything that happened so far is all part of Luke's plan and it's just the worst plan ever. Either way, Luke is the final stage of the plan, almost as if he's let his friends give it their best shots and now the only Jedi in the crowd has to step up to show them how it's done (to no real effect).