Unless you use a film with an extremely clear base, I would think viewing the image through the film base would show more base and fog density than you would like. You have some variables here to experiment with - film (or other substrate), exposure, development, developers, bleaching, final mount. You might experiment with liquid print emulsion on black glass or plastic, if you can find a way to make it stick. Transferring an instant film emulsion to a black backing might work. You're just going to have to roll up your sleeves and try it!