That's practically what Gary Kurtz said in interview. He didn't say anything about Fett though. Interesting...However, from the interviews of the time I have read that ESB would see the introduction of a new main villain, which was obviously Fett. Marvel seemed to have a much better idea of what ROTJ was originally going to be like with their "Crimson Forever" story, which showed a big search for Han.
http://vignette2.wikia.nocookie.net/starwars/images/9/9b/MSW50_Crimson_forever.png/revision/latest?cb=20130309221844
At the end of ESB Lando said, "Once we find Jabba the Hutt and that bounty hunter we'll contact you." In other words, at the time ESB was made they didn't know where Jabba was. He certainly didn't live on Tatooine, otherwise Luke would've known. Crimson Forever was taking that line by Lando and them flying off into the distance as if there was going to be this big search through the galaxy, which during the making of ESB there undoubtedly would be. It's only once ROTJ came around that Lucas got lazy and plonked him on Tatooine.
Chances are if we'd got the ROTJ originally planned, Fett would've had much more dialogue. He would've truly become an "evil Clint", with a much more developed character.
Kurtz said he would've been rescued half way through the movie, then would've sacrificed himself on a mission against an Imperial installation, probably much like George Peppard did in Operation Crossbow.
https://www.youtube.com/watch?v=uGSMuLr2nqc
It would've been sad but also heroic. Han would've gone out a real cool dude! That's why I'm right behind Kurtz with what he wanted for ROTJ!
Yes, he probably would've been developed further into a battle scarred ruthless type (hinted at by his original voice), a bitter vet of the Clone Wars. Chances are he would've even taken off his lid at times during the movies as well.
When he did care, Leia would've left the movies at the end of ROTJ, after the death of Han. Luke would've then gone off alone in search of his sister (i.e. The Other), who would've been a Jedi in training on the other side of the galaxy. Once he found her, they'd both team up to confront the Emperor in the Imperial Palace on Coruscant in Ep. IX.