Remember they would have had to triangulate between [the director], the script, and the other actors...
That is a challenge, but not one unique to the role of Leia. So I can state with confidence that lots of other actresses could handle that challenge, because they already have handled it, repeatedly and to great effect. There's no magical Venn-diagram of "performer traits" and "traits needed to be Leia" in which Carrie Fisher was the sole inhabitant of the overlap.
You make it sound like it was easy to do what she did in Star Wars when frankly if you read much about the shooting of Star Wars seems rather not true.
I didn't make it sound like it was easy. Nothing I said implied that. "More than one person could have done this job" does not equate to "this job was easy".
Any other name you put up would either have no chemistry, have quit or hung herself after a week.
Any other name? Come on. Would you suggest that Sigourney Weaver couldn't have chemistry with Mark Hamill and Harrison Ford, or that Meryl Streep couldn't handle the stress of making a Star Wars movie? If not then your claim is meaningless, and if so I'll start laughing now and avoid the rush.
Say what now? I had no particular counterpoint in mind. What point did you make that you expected a counter for? Or do you mean something about the prequels? I don't really see how that's relevant as the situation is so different...
It wasn't directed at you specifically, more at anyone in general who would have said "But what about Hannibal Lecter/Indiana Jones/whoever?". Because the same point applies to those characters too; yes, so-and-so did a wonderful job, but there are other people who would also have done a wonderful job.