If you want a thick film, and can shoot 120 film use Verichrome Pan. Next, the primary reason film reticulates is because of a temperature difference between solutions - going from warm to cold. In warm water the gelatin swells, and in the cold water it shrinks rapidily, stretching it apart.(posted 8733 days ago)Now, most fixer has a hardening agent in it. The hardening agent causes the gelatin molecules to cross link making it swell less. If you want to reticulate film, I would use a non-hardening fixer on the film. Then put the film in a water bath at about 90-95 degrees for about 1-2 minutes, then put it in ice water. After it reticulates, I would refix the film briefly in a hardening fixer, or put it in a hardening bath and then carefully wash the film.
Unhardened gelatin will start dissolving/melting at a little over 100 F so you will have to be careful with the temperature of the warm bath.