I think the penetrator tip should be a full time option, even on the website regulars. Simple easy mod to put on when sharpening.
Coatings and handles, those are a staple.
Spine changes should be model specific - due to additional plasma/water cutting requirements and programming. Obviously anything offered with it originally they have a file for it, but anything pre-offering would have to have custom files made. Plus to keep machining costs down and turnaround up....you would have to have it model specific.
What would be cool to have is a custom pin/rivet option. Doesn't really take away from the manufacturing process, but adds something custom to the blade. Kinda like having the custom shop open, but not.