I'm back for round... 4, is it? It's been too long.
1: The only aspect of the Turaga, Toa Mata and Toa Nuva sets that truly frustrated me was that I tried so many times to seperate brainstalk and faceplates, hoping that they could come apart and be recombined. We should've been informed from the start, and yes, this is a bigger problem than "posability."
2: The greebled texture of pieces is a good part of what makes G1 BIONICLE sets so visually interesting, and I love that. Working with those same pieces now, I'm noticing more and more how those little details interfere with the area around their connection points. Looking back, I think LEGO should've more heavily weighted MOCcability in its piece design process.
2.5 That said, the Toa Hordika introduced what are probably the most satisfying pieces to work with– the breastplate is great, both parts of the jointed arm make good starting points, the two-toned weapons and unique helmet-y masks are fun, the necks are indispensable, and the main torso is just the right mix of a body shape and wonky technic block to be deceptively versatile.
3 (This is in response to the SW Buildable Figures line:) If LEGO wants to keep constraction going, what they should do is come out with parts packs. For one, we need some new model shapes– and there's only so much innovation you can have when you're determined to stick to human proportions. I don't mind the idea of common CCBS skeletons, but if they're all the same size and shape, they might as well have the pieces for two figures, with one built at a time, in a box. They've pretty much all got the same innards, right? New pieces could come in smaller sets, even bags. One thing we definitely need to see is a new foot design. Feet are textured on one side and flat on the other; that makes them great armor, connecting or covering pieces. More experiments in armor design would be great too, we'd get greater variance in shaping that way. Bottom line here is that LEGO's gotta starting bold again if it wants to cater to us incoming adult constractionists. If they don't we'll either fall away or do it ourselves.