typical fecal transplant won’t cut it here. although conceivably one could engineer one of the critters involved to “preprocess” for you. not sure how long the required enzymes are active in refrigerated liver (data is probably available for mouse liver), nor how well they would work in the acid digester they would be meeting the cannabinoids in…seems like a (very) long shot.
I’d suggest trying a “raw liver based edible” (THC infused foie gras?) if you really want to pursue this.
There is a hand held genegun that (iirc) showed promise for direct transformation (of the liver!) some 20 years back. Just make an incision, shoot em in the liver, sew em back up. (Particle-mediated gene transfer into murine livers using a newly developed gene gun | Gene Therapy)
Going in and grabbing some cells, culturing, transforming, then reimplanting would be a much better approach imo. If you were looking to solve this permanently.