Uh ... yeah, spoilers. Wouldn't it be easier to mark the thread with spoilers? I mean, honestly ...
The Collectors struck me as very ... tragic. Forced to do the Reapers' bidding by creating new Reapers, all that. Basically, desperately trying to make up for their own "failure", in a twisted way.
I never really got the impression the human Reaper plan was something on the official Reaper agenda, more like the actions of Harbinger using the Collectors. But that's just me. Either way, it does seem they want to make a human Reaper, and that the timing of such a creation doesn't really matter. Using it to attack the Citadel, like Sovereign tried before, doesn't seem unlikely, but it seems unlikely such a plan would work a second time. In the end, it's not something that bothers me a lot, so if there's no official explanation ... which I don't see as that unlikely, then ... well, hey, I have my own theories, and we can be happy not knowing and all that.
As for the form ... well, like I said, tragic Collectors and all that. I saw that basically as an expression of ... well, the Collectors worshipping humans, almost. They were deemed unworthy, but the humans are worthy, so in some twisted way, they worship them.