Lets be honest..
I think whoever is the one to save luffy Will be something interesting....but not THAT hype as some people are imagining.
Lets Just think a bit...
If was a big shot as Garp, the Great fleet, Dragon, Shanks, Kuzan, Sabo, some revolutionary ,etc that would finish the chapter, not be in the middle of It.
And Redon/Lance would be way more crazy about It than he looks right now, even with that bizarre oden reveal he was way more active.
I think It will be some Sea kings...
If not that, will be laws crew, Hyori, Kawmatsu, izo or Denjiro since they are not fighting anyone, that Fox dude, the octupus
,the carps, tengu Dude.
Something like that..