It's just the same as with ISO (international kit). It does hit its MOQ with specific amount of sold base kits. So it does not make sense to introduce that kit if say only 300 base kits are going to be sold. I can't predict how well GMK Toxic will sell and there are enough other group buys where people will have to make choice what to get.
Is that really the case? MOQ of a child kit directly related to the MOQ of the base?
I kind of get your point, but I dislike the pessimistic approach - "this will probably not sell too well, so let's not even try". I realize there's some extra effort needed to put together the kits, but I'd expect it wouldn't be a problem for you as a seasoned set designer.
Anyway, I won't bug you any more. I just have a feeling that if 40s/ortho is not introduced right from the start it's not happening. But as you say, plenty of other sets to choose from...