This a long thread. Never the less I read it. I have fed my mantids dead bugs before by tipping the enclosure upside down and manipulating them to strike at the dead bug by making it look like it is crawling down the side of the container. I just did this the other day with my friends blue flash and a uncooperative waxworm. I would imagine if your friend can find a protein source maybe they can try this technique.
Sure tofu or chicken breast or cheese. Hmm, I wonder if we can make a super mantis with a high concentration protein diet. Wonder what the protein content of a cricket is so we can use it as a control. Maybe we can improve mortality rate with offspring. Who knows maybe they will start using primitive tools and cooking with fire.