If there's a chance that the Government or some other entity will come after you for whatever you're doing on Tor, and you don't want there to be any way that your machines (clients or servers) could leak their public IP address, you could put them behind this.
They can deanonymize you at the NSA's scale. They can deanonymize you with browser exploits at the FBI's scale.
If you are going to be actively targeted using Tor is not sufficient.
Tor is an effective defense against passive, generalized surveillance. It isn't effective against FBI/NSA-level resources because they will just drop 0 days in your path until you get hit by one.
We know of at least one Tor hidden service which was deanonymized because it leaked an IP address at some point. This protects against that flaw being likely to happen again. That is what the use case of this is. Of course it's not enough on its own. It protects against a specific attack in an easy-to-setup way.
IF you were serious about this, setup a router to TOR correctly using quality hardware. Use a router distribution (e.g. PFSense) on real hardware. Otherwise, you'll be just as screwed because your service will be ridiculously slow.
This wouldn't be able to handle anything more than a consumer grade internet connection at relatively low speeds.
"By our fourth round of prototypes we had created a model with 64mb memory and a 580mhz CPU. This not only runs the software well, it flies! At last happy with the board, we designed a simple, minimalist case in plain white to house it. The end result is our current model. We decided to name it the anonabox."
Running CPU intensive processes (e.g. encryption) on a high throughput connection (e.g. web server) isn't going to work unless its only used by you and your 5 friends.
If there's a chance that the Government or some other entity will come after you for whatever you're doing on Tor, and you don't want there to be any way that your machines (clients or servers) could leak their public IP address, you could put them behind this.