I know wat you meant, imagine robin with armament haki, summon arms with it, DONE!!! that is why I compared rebecca with her to begin with. The next chapter is really what we need to tell how strong rebecca truly is, however being a relevant participant and knowing how she is not going to drop right off the bat, is enough to give an premature estimate that she is strong! in her on right! which makes her a very viable candidate on taking the mera mera fruit.
I also doubt, that any current member of SH will take mera mera. Because, their character is already developed, they have their own fighting style. Oda will not add a layer of mera mera ability to this character, which without a doubt will overshadow their already developed skill set.