Correcting one thing here, this isn't a 2007 makuta design it was a 2001 concept for makuta "teridax" In Faber's post he comments "Looking back at my 2001 sketchbook." This design was most likely one of the original designs for Makuta Teridax and as it appears did not make it into the final story.
My own thoughts on the post so far.
May be reading to much into this, but I think he told us more than you'd think.
First off what we do know from this post:
The hollow chest makuta is an idea, concept for makuta original since this comes from his 2001 sketchbook. Second the design of the makuta is strikingly similar to the promotional "M" artwork, the "M" circle sketch also resembles the symbol for the makuta phantoka, perhaps this was an inspiration.
From reading through his post, Faber is going to harken back to some old concepts and give them new light. From what it sounds like he's incorporating old ideas into his "Bionicle"
Theorywise: I think he's going to give a bionicle more similar to what the early days gave us.
with six heroes cast away on a strange island full of wonder and danger, the makuta will probably be the only of its kind, perhaps the rest died off or something to that effect. Perhaps he'll take the metaphor that started his inspiration for Bionicle and change it into what Bionicle means to him now.
Whatever it is, I'm kinda more excited now