I want a black person with dark brown skin and blonde hair and green eyes.. male or female i don't care, the hair should also be straight or stringy curly. even dreadlocks are acceptable, get on it BioWare, I demand representation of these mythical beings.
I actually really love the contrast of dark skin with light colored hair and eyes. So, while I wouldn't demand it, I think it would be cool if it were to happen.
Which is probably the ultimate reason for the absence of ingame blondes. It just looks as if someone slapped a straw mat over the persons head.
I'm no computer nerd, but in this day and age it should be possible to use highlights and shaders to create believable hair structures.
I think a lot of the ME lore was initially dictated by the limitations of the engine and the budget. The Asari might have been monogendered either way, but it looks like it also helped them save on creating different character models. It was practical to only have one type for each alien race.
When it comes to things like believable hair, it might be a really minor concern, but it can create a distracting contrast when the faces are fairly lifelike and expression, but the hair still looks like a stiff helmet with no depth or variation to the color.