I'm torn on this, as this alt is a human-miraluka hybrid (which is canon) and I RP the offsetting weaknesses as I recognize that messing with genetics in this way can be detrimental to the offspring. For example, this character does have human eyes and utilizes 'Force sight', but she can only optically see in monochrome and can only sense proximity of objects and not mass or shape.
However, I have seen people try to stuff every last bit of power breed into one person, which really makes me not want to RP with them. I understand that I have a choice to not enter threads involving such characters, but if I were to enter a public thread or invasion, there is nothing stopping them from entering and engaging me at that point.
It's a very tough issue. My preference would be to restrict to 2 species. But in the spirit of allowing for a little diversity in an RP community, I might propose an Option D: Restrict to 4 species - one for each grandparent. Anything beyond that would be ridiculous and 'inherited' special abilities would be ignored. And please use commonsense.