I would suggest you all lighten up honestly - Takara didn't differentiate the parts, they're all "F230", and we've already condoned cleaning them out, which requires disassembly. If it helps those who can't get a Takara Orange one improve the performance of those they can get, then it strikes me as a good thing.
A ban on it would also suck IMO because a fairly common breakage of any track is the threading area, and if that happens to a Takara Orange one, it could feasibly be replaced with a cheaper one without affecting the performance - quite a handy option, no? Same goes for a lot of parts, even those where it might affect performance like the rubber on R145 (soft vs hard) or those extra-free-spinning ED145's. There's also CH120 which aside from being very breakage prone tends to vary in tightness of the locking function, and mixing/matching parts could help there too, perhaps - in that case the difference doesn't seem to be due to color, just random variation (presumably the locking nubs being slightly larger/indentations slightly less smooth or whatever) so you could get more of a difference mixing and matching identically colored parts.
If Takara expressly forbids disassembly in MFB (in that case one would expect them to use Triwing screws at the very least, though), then perhaps that is the case, but unless that's an explicit rule, it strikes me as needless restriction without any gain - not even professionalism, tbh.
Lastly, there's the fact that parts can be dyed - risky and IIRC Ingulit tried it with something and it made the part very brittle, but that may just be a temperature thing. Still, it would mean someone could simply take the differently colored parts, dye them, and no one could tell - basically such a ban would only be enforceable because the difference coincides with different color, which seems quite unusual to me.
Oh, there's also the whole thing with the 4D LDrago Cores - there is variation there and we allow them to be swapped, and they're not even necessarily called the same thing (there are other instances of recycling, SW145 and UW145 share a centre part, for example).
Of course I tend to be rather liberal about these kinds of things, especially with my background in plastics, so perhaps I'm way off the mark.
@Aquamarine: Are you basing that on a comparison to an orange one you own? Personally I think that if the friction is enough that wear is occurring at such a noticeable rate, then a brown one could never compare to a Takara Orange one even fresh out of the factory because it must have more friction and therefore would perform worse.