I just can't see it being immersive if you choose the shape when you place it instead of when you craft it. To me, that seems worse than changing a metal reinforced wood block into a concrete block which YOU have always been critical of.
Can a meta tag be used to decide if a block looks one way vs another way? Lets say I just swallow the bile in my throat and agree to just craft a "master frame" (whatever that's supposed to look like) and then when I go to place one I call out loudly, "Form of....wedge!" and then when I place another I proclaim, "Form of....pillar!" so that I transform the master frame into those two different shapes on the ground in front of me.