I can see your point. Looking at the PAC it seems that IM: Characters would prevent that character from carrying other characters. But are there any such characters?

Hank Pym and his particles can give anyone with IM: Characters the ability to carry.

Once they add Improved to the search filters I can answer this more fully.

hehe Well the existing of such characters isn't really relevant as you've point out you can still create the situation. Perhaps it's one of those negatives wrapped into a positive.