Sounds like an interesting idea. After all, people have loved how TMBTM grindhoused Star Wars and Jaws... you might even consider using that for some ideas on how to make a grinhouse version.

In any case, the B&W to Color transition, as well as aged film, sounds interesting.I vaguely recall there was a special feature showing stop motion dinosaurs in the DVD. Maybe you'll want to include those in some scenes to replace the stunning CGI? It would be understandable for grindhouse producers to suddenly lose money and have to resort to stop motion for a few dinosaur scenes.