Some of everything. Here’s a rough mockup brought to you by the finest free online image editing websites I could find:
I chose the Uniter Mask of Water for Gaaki because, for some reason, I’ve always associated that mask with her more than the actual G2 Gali set.
Standard Shelek for Bomonga for two reasons: I think it would be cool to give one of the Hagah a new variant of an existing mask, and Galva’s Shelek really worked with the “big and tall” vibe that I’ve been thinking of for Bomonga.
Khingk’s Mask of Psychometry as Unknown Kanohi purely because I really like the shape. And the squarishness fits with short/stocky Pouks (sorry I couldn’t capture his thunderthighs. Maybe later).
And then a Hau for Kualus because I figure at least one of them should use a pre-existing G1 Kanohi, and the Hau is pretty much the most iconic one there is.
When it comes to new vs. old designs, I think we should go for a balance; it would be a shame to not take advantage of the opportunity to do something new (even if they’re just variants of existing masks), but it would also seem a bit too convenient if all four of them happened to have never-before-seen Kanohi.