First of all, I'm pretty much a newbie with MakeHuman so I don't claim to know all the trade-offs between different ways of dealing with racial features, especially the programming aspects, I'm just giving my perspective as a user interested in parametric sculpting, I don't know if I could do better or if my ideas would work well if implemented. This is just my reaction after a week or so of trying to "sculpt" some Asian faces with MakeHuman, take it for what it's worth.
I see the race sliders as offering three "prototype" heads representing recognizable instances of people from three races. The first problem with this is the whole idea of "race" is known to have a poor fit to reality. The variation within each race is so vast that you can't really produce a single prototype for any of the races. Rather than Asian, I think it would be much more realistic to have a gallery of faces to choose from, like Northern China, Southern China, Korean, Mongolian, and a few Japanese variations. You could also have feature-specific racial features, like "Asian eyes", "Southern African noses", "Northern Africa noses", as well has having variable skin tone, etc. etc.
At very least it would be a gift to have a fourth slider "Base" so that you could get a neutral head if you want to start from scratch. Right now, a target made with the base mesh in MakeTarget is almost certain to be messed up by the gender and race settings.
Alternatively, since, other than height, the racial sliders don't really affect the body at all perhaps they could appear on the face tab rather than the main tab, maintaining the base head until one starts facial modeling? In fact, it might make sense to rename Main to Body (and Face to Head) and more fully separate the body and head modifications. As an example currently Weight in the Main tab only affects the body and there is a Head Fat slider under Face/Head Shape. If Main is meant to be global then it should probably incorporate some Head Fat as it makes the body fatter, but I think generally global is the wrong direction to move in.
Similarly, I would much prefer to be able to adjust body gender without affecting the head, and maybe have a gender slider under the head tab. Here's an example of a peril of mixing race and gender:
For the Asian skulls, the back of the jawline is more slanted for the female and vertical for the male, while for the European skulls the opposite is true. So when I model an Asian, in order to get a male body type I end up with a female jaw line. Arghh! And of course those skulls are again just representative, a good portion of male Europeans also have a more vertical jawline.
I'm going on too long but here is an illustration of intra-racial diversity/inter-racial similarity:
Excepting the eyes, this could be a Neo-classical Greek sculpture with its geometric smoothness and simplicity. It's a lot like the base mesh, but is pretty much impossible to achieve once you have set gender and race on the main tab.
Going back to skin tone, it would be a very powerful feature to be able to supply a secondary skin which would be merged with whatever skin is being used with for example an opacity slider. You could use it to affect skin tone as well as add surface features like the eyebrows in the special suit skins, as well as thing like tattoos. You can already do that by creating a new skin, but if you could composite multiple images you could produce a tattoo and use it with any of the base skins (young, middle aged, old, Asian, Aftrican, Caucasian, etc.) without having to produce a separate skin for each. You could also produce skin tone modifiers, and do things like color lips or other body parts.
I just wanted to put all that out there.