Most mantids are cannibalistic but some do well in communal habitats under certain conditions. I have studied this for years learning which species and how to control the environment successfully. Certain species are more amiable to communal living. Less aggressive predatory mantids such as ghosts, dead leaves, etc. who don't stalk prey are the natural choice for this type of rearing.
The types of mantids I recommend for this are in a category I refer to as the "Pinheads", those with tiny heads and mandibles are the obvious choice.
Habitat is key and should allow as much area as possible for the group to get along without disturbing one another's space. Creating canopies, perches and hides to accommodate the different sizes and stages of males and females as would be similar to the environment in the forest which they inhabit in the wild.
An abundance of food is also crucial, excessive feeding can ensure success
Here is a link to a study on how mantids act within communities, in interestingly cannibalism is greatly lessened when the group is made up of siblings.