There's been some really lovely OBWs and 4PPs created with minimal colour variations. Sorry, I can't give you links, but one I remember was a fairy fabric, posted by LuvE. Another was a light turquoise and brown combo, no clue as to the poster, and the brown gave a lace-like effect. I think both ere 4PP, and certainly were stunning, and are the reasons why I think your fabrics would do a great job.
As for your comment about carefully cutting to get the uniqueness. Just continuously cut, whether for 4PP or OBW, without any thought about the results. That's the uniqueness of this technique. Every posey or hex will indeed be different. If you do a repeat of the pattern, then slice an extra inch or so off before you start your next repeat, to ensure new kaleidos are created.
One thing that hasn't been mentioned, yet I'm sure those fabrics are OK ... how far apart is the repeat?