You can't say with any authority what they did and did not have planned, or what did and did not end up on the cutting room floor. You're purely speculating, whereas Yoshida is literally telling you they had plans, but they cut and rushed things.
As Hallarem said, there has been plenty of people saying over the years, "NUH UH THEY DIDN'T HAVE A GARLEMALD EXPANSION PLANNED YOU'RE JUST A FASCIST WHO WANTED THEM GLORIFIED". Especially since I could never quite find the interview where it was previously mentioned that this was true. It was always dismissed as a fanwank "rumor". Now here it is, in print and indisputable.
To that point, can you provide a source saying they "all agreed Zodiark shouldn't be the last boss"? Because it seems like the perfect cliffhanger leading into patch stories. Kill Zodiark, ominous red color, mysterious voice saying "Ah...at last!", Final days commence, how is that not literally perfect cliffhanger material? Again, just like the other guy, I think youre making an assumption, and you don't know what they did or did not plan. Besides, just because something is predictable doesn't mean it's bad, and just because something would be "subverting expectations" or "a bold choice" doesn't mean it's good. The Last Jedi certainly "subverted expectations" and was definitely a "bold choice"... doesn't mean it was actually good.