That’s a good idea, but I’m afraid that one of the two sets of prongs (one from each half) will not fit on the current head when worn in combined form. 
To illustrate my point:
This would be problematic, unless one half is so big that the prongs of the other half are nowhere near the head when two halves are combined.
Yes, that is exactly what I mean. Only the possible bottom half would end up connecting.
or the first mask can have a part where the second mask’s prongs connect
The top part could connect like the Garai, and the bottom like normal.
that’s a cool idea, but it would make it a pain to take off the top half
Maybe this is why G1 masks connect to the mouth and G2 masks connect to the top of the head?
So, just want to point out: what if the Vahi wasn’t forged by Vakama? Rather, it was simply put back together after breaking into six pieces?
~W12~
I agree with this. Add to that the costs (both time and money) of designing a mask combining function for one mask? I don’t really see it happening.
What I would predict is this:
As shown in the graphic novel and hinted at at NYCC, the Upper Half of the “True Mask of Time” is the G1 Vahi.
This would confirm that the Toa are drawn from its home universe of G1.
The Upper Half will not get a set release (the Vahi is an obsolete part).
The Lower Half of the Mask of Time is a new G2 mask, basically G2’s Vahi.
It is added to the story only as a plot device to allow the (completed) Mask of Time to get a set release later, without contradicting the Mask’s earlier portrayal as the G1 Vahi.
The Lower Half will not get a set release (it is not significant enough to the primary story [unless it is actually the MoUP, which is possible ;)]).
The True (completed) Mask of Time will result from a fusion (in-story) of the half masks, and resemble a mixture of both, though will not separate into parts or anything like that. (Why would it? Did your G1 Great Kanoka actually fuse into the Disk of Time? 
)
This gives narrative symmetry - a half from each generation, forming a link between them.
The True Mask of Time will get a set release. (Winter 2017 or Summer 2017 [depending on whether it is formed from the MoUP as a way to complete the story arc].)
One thing, the GN states that the G2 mask is the “upper half” of a mask.
Well, not necessarily. The Toa might be from a different universe altogether. Though I doubt it. That would mean there’d be three separate universes – G1, G2, and the one the Toa came from – and I don’t think LEGO would go that route. So if there is a connection between the universes, then yeah, the Toa will probably be the G1 Toa.
~W12~
I’ve been saying that for a while now. Great minds think alike.
Don’t you mean the bottom half?
It states that the half owned by the Protectors is the Upper Half, which is illustrated as being the G1 Vahi.
Nope. Upper Half doesn’t necessarily mean the mask covers the forehead.
For example: (I think the left idea is most likely.) 
So it’s worn differently in G2 than in G1?
but that leaves out everything post phantoka, and even then leaves out crucial story details
(each half sold separately ask parents before going online)
