
What if R2-D2 and C-3PO had fallen directly into Ben Kenobi's hands.
No splitting up and being picked up by the Jawa's, no being sold to Uncle Owen, no coming into Luke's possesion and no playing him Leia's message, intended for Kenobi.
What if R2 and Threepio had found Ben
without the involvement of Luke Skywalker?
Think about it. Bail Organa gave Leia the task of contacting the elderly Jedi Knight with the intention of bringing Ben out of retirement to fight alongside Bail, his old friend from the Clone Wars. Bail wanted Kenobi to help him with the cause of the Rebellion.
Nowhere in that mission statement did it mention the son of Anakin Skywalker (which, don't forget, Bail knew full well was his adopted daughters twin brother).
So, let's say R2 had found Kenobi straight away. Would Ben have had any need to involve Luke?
As things occured, you could say that Kenobi allowed certain events to play themselves out, namely the deaths of Owen and Beru (Luke's last ties to Tatooine). Ben knew Owens feeings on Luke's heritage and knew that Luke, being a loyal boy as he was, wouldn't have left Tatooine without their blessing (don't forget, all his friends had gone and yet he still remained. Obligation to his family was what kept him on the Moisture Farm, and both Ben and Owen knew that).
So, what if Luke hadn't been brought into the equation? Would Ben have gone on his mission to Alderaan alone?
We are told by Ben himself that he was "Getting too old for this sort of thing," but then, he would say that wouldn't he. He was trying to persuade Luke to leave everything behind and join him on a crusade to Alderaan.
So perhaps R2 split up from Threepio for a reason.
From what George Lucas himself has said, Artoo knew
everything that had transpired. He never had his memory wiped like Threepio (on the order of Bail Organa) and so Artoo knew that Luke was under Kenobi's care on Tatooine.
And Bail knew that too.
So why send those two particular droids, with his daughter (Luke's sister) to Tatooine? Did Bail want Ben to come alone, or was he hoping for more than just that?
Bail called for Kenobi, but he
knew Ben was watching over Luke.
In an indirect way, was it Bail Organa who made the call to bring Luke to the forefront of galactic affairs? Not the last two Jedi, Yoda or Kenobi, but Bail.
If so, you could say that it was the masterstroke manoeuvre of the original trilogy.