My opinion on this project:
I would prefer to have buttons made either using Investment casting or Plaster casting. If Investment casting is not possible, then Plaster casting would be the way to go, even if it might be somewhat expensive. I wouldn't want to put some low quality buttons (or painted plastic for that matter) on the empeg. Especially if aluminum faceplate becomes available, and it looks like webroach is doing pretty good job on those, it would not be a good combination.
With regards to the buttons' design, they could have some embossed/beveled profile outlining some soft of embedded arrow or round circle (a point). Or, going even further, the buttons could have small transparent plastic inserts for the lighting kit.
Regarding the knob, it's possible to go with machining process if it gives good results in recreating 303's NewKnob, though I'm not familiar with the process he used.
One thing need to keep in mind that these buttons/knobs eventually have to be compatible with lighting kit and aluminum fascia.