a) performance hit (camera based sorting + blending for non-translucent blocks, iirc solid/cutout has blending turned off)
b) shaders being stupid and bigger performance hit, example: https://discord.com/channels/472875599422291968/472879361800929290/943173427416694794
problematic code: https://github.com/ldtteam/Domum-Ornamentum/blob/version/latest/src/main/java/com/ldtteam/domumornamentum/client/event/handlers/ModBusEventHandler.java#L62

The problem is how to either define rendertype per block instance or how to connect two instances of same block (one cutout, one translucent) together in way that end-user can't see

Side note: if not yet possible PR into forge: allow block to use more rendertypes -> block rendering methods would need rendertype based variant

Not solveablke at the moment without more fancy systems. Impact is negligent.

Basically the render type selector does not give you the block entity data. You would need to generate a new model per render type like i am doing with candb which is possible, but not something i am planning to add since our current system does not support discarding vertices from the geometry.

As such closing as technically not feasible.

Hit me up on discord night if you want to talk about this.

Illustrate one of the side-effects when rending solid blocks in pass-2 (translucent). The "I need attention" icon is overlaid by domum_ornamentum solid blocks rendering as translucent: