I'm still waiting for a salient reason why they shouldn't have used the dice as a symbol of the character.
What should they have used in their stead? His blaster? His old jacket? No. The dice are the perfect symbol for a damn near pathological risk taker.
No, sorry, that's absolutely not the same. Jabba was always integral to Han's backstory in the OT. They didn't just "decide" to put him in ROTJ for the hell of it. He was in early versions of the ANH script. Jabba is why Han wasn't going to join the Rebellion in ANH, that's why Han was carbon frozen and taken back by Fett, etc....
Jabba = Dice. Seriously.
This may be difficult to grasp, but broad comparisons do not always translate to 1-to-1 equivalencies. Adjust your thinking accordingly.
And yes, again, they did "just decide" to put Jabba in there, it's just the decision was (provisionally) made when writing and editing ESB. The Jabba debt was something they didn't have to carry forward, they could easily have just assumed Han had paid that debt with his reward money as was his stated intention and not ever bring it up again.
Indeed, in early drafts, he was only mentioned in passing and not at all related to the plot. The major thing with Han was initially going to be some meeting with his long estranged quasi-adoptive father from whom the Rebellion needed a favour.
They however chose to build on what was a minor plot point in the first movie and carry it forward. (Remember, the Mos Eisley scene was still on the cutting room floor at that point and thus didn't need to figure into the decision.) Again: an extrapolation. RotJ built on it even further by actually showing us Jabba and bringing that thread to a close. Again, they didn't have to and again, in early drafts (when they weren't sure Ford would return) no Jabba to be found.
He only seems intrinsic to the trilogy in hindsight, but really he could have become just a passing mention at any point in the process. No more significant than the Kessel Run, the Clone Wars, Dantooine, the Battle of Taanab, the Bounty Hunter on Ord Mantell, or Ducain and the Irving Boys.