While I do think the shape might be workable depending on the person, ToyGeek is absolutely correct on the material. You would need to use a condom on it every time. I second the recommendation to choose something made of silicone. Tantus, Happy Valley and Vixen are all fantastic manufacturers that are sure to have something you'd like!

Also, I just posted in another thread about this, and will reiterate it here. There are better harnesses out there than the Vac-u-lock type. Those will require that you forever purchase their proprietary dildos, which can be in yucky materials. Your best best is something like a Joque or Rodeoh, or an exchangable o-ring harness. These will let you use any toy of your choosing, which means you can pick a lovely silicone piece that will last you a lifetime!