The color system works because:
- it's done for higher volume cameras (K-50 level)
- it takes almost no R&D effort (just to decide the color, and make sure it's strong enough)
- it takes no extra production effort, i.e. it keeps exactly the same production process except tracking of different colored (but otherwise identical) parts.
There's no outsourcing involved compared with the "standard" bodies.
OTOH, to build a feature customized camera would be a much bigger effort, and I doubt people would pay more for not having a top LCD
I don't like the idea of a "FF" 645D; the result would be a larger "FF" camera using much more expensive slow-ish lenses (and no, those on eBay don't matter). Doesn't solve a problem, but introduces many. Can't work.