I'm no expert of course so I don't know if you've tested it on meat at it worked? Being slanted is an improvement but it seems 3 blades could never replace one longer blade, the points might get caught and create piercing holes instead of allowing it to slide down and slice. The blades themselves also look too short and might just create a cut stopping at the plastic instead of going through. And can it support the weight required, because it will probably have to be quite a bit.

Anyway my idea was mostly just a morbid thought experiment, and on second thought you likely wouldn't be able to acquire it easily but eh. I was thinking one of those old large tabletop paper cutters would be effective: https://i.pinimg.com/736x/ac/86/12/ac861229a740a2b5abea72ca1e14dcd3--vintage-paper-school-uniform.jpg It's already basically a guillotine, with a very secured, heavy, and sharp blade. It would need to be modified by removing any safety features and the spring in it that slows its fall. A very heavy weight could be attached to the handle and could sit on something that could be quickly pushed/pulled when ready allowing the weight to fall off a table. If needed a plastic shield that sometimes comes with them could be put in front of someones face with a hole for just a tongue (yknow to prevent a nose being cut off). Even a rubber mat could be put on the cutting area with the tongue stretched out and pinned down at the end to secure it like on a dissection table, which would hurt but not as much as the actual slice. Kind of fun to think about but who knows if it would actually work.