Thats a very good point.
Back in the original version of Return of the jedi, Luke does meet his father on the imperial city (before it was Corrasant) and get taken to this huuuuge pyramid call ed the imperial palace and get taken down the elevator and meet the emperor in the lava caves of the planet where the emperor sits on his throne. Eventually Luke does kill his father and joins the dark side in another epic twist.
This info has been confirmed by Lawrence Kadan and Gary Kurtz who wanted to do another epic movie to finish the trilogy, along with the other ideas such as Leia becoming queen, Han dies and Luke walking away in the sunset like a western.
All this would tie in nicely with the journey of Luke from Degobahs cave scene and him rescuing his friends and knowing he might join the dark side and destroy everything he stands for. and then ......boooom the hero we have journeyed with all this time eventually succumbs to evil and this would be an epic ending to the series.
Of course the original version would never come to life as Lucas never wanted to go through the tough times of the first 2 movies , what with budgets, delays, script rewrites. Lucas was going through a divorce which was costing him loads of money and I guess he turned his mind to making loads of money from the merchandise. It was a bad move for the movie but I kinda feel sorry for him in a way. These movies were hard to make.
As of today however. it turns out that maybe this idea of Luke becoming evil may actually happen!! here is what has been reported today from comicbookmovie.com
MAJOR SPOILERS AHEAD.
"One piece shows this cloaked figure holding the helmet of Darth Vader. The helmet is warped as it has been burned in a fire. The figure almost looks at the helmet with remorse and regret. The background in this image is an Imperial Star Destroyer. The monster holds the helmet in his left hand while his right hand is shown to be very similar to Anakin Skywalker’s and perhaps Luke Skywalker’s.
The black figure sits on a throne. He’s cloaked. We see him from the side. His boots are not unlike Anakin Skywalker’s from Revenge of the Sith. He is approached by “Kira.” The light from outside the shrine emanates from the door way and she walks through it. The cloaked figure sits in darkness, a natural red/yellow fiery light behind him, almost like amber backlights the figure. According to a source, “Kira” believes she is there to meet Luke Skywalker, but instead she finds the monster. In another depiction, she is facing the camera, the cyborg character is embracing her and the look on her face is one of resignation and defeat. We are looking over a character’s shoulder, of what is believed to be Boyega’s character.
So why does “Kira” appear to give up? The reason for her resignation? The cyborg is none other than Luke Skywalker. The revelation beats “Kira” and her quest becomes hopeless. She resigns herself to joining the figure who is the opposite of what she hoped to find. The evil she sought to vanquish with the power of Luke Skywalker, is Luke Skywalker. We are left not knowing the future and how this happened. The cloak appears to be especially close to Luke Skywalker’s Return of the Jedi cloak as well."
Put it this way. Lawrence Kadan is the script writer for the new film and he really wants to take the new film back to the spirit and heart of the originals. So its possible that this idea will continue on now that Lucas can't stop them now. :)
however, with Pictures of Mark Hamill growing a huge beard, it doesn't quit makes sense with the picture and description put together with Mark Hamill's bearded look.
But who knows. it may be false. But I actually would really like it if it was true as it would tie in nicely with Luke's journey from the very first movie up until now. It would be a a damn great twist and would make sense with the Siths return in the movie rather than it being someone else.
Even so, you made a very good point about that with Luke wanting to take risks he does in order to be powerful. Thee are some amazing physiological points and themes to picks out in the original movies which is what makes star wars very entertaining and interesting t watch :)