While you certainly can use a rpi and Debian (or Raspbian), there are reasons why this may not be the best solution. Basically a router is just a computer and often the software the company producing it often is a linux OS and many of these commercial router boards have processors and ram that are way less than a Raspberry pi.
However, most of these boards designed to work networking have special hardware acceleration for traffic. It's basically similar to how a desktop computer can have a dedicated GPU for doing graphics, but it is some chip-set that offloads the network transfers from the main CPU. In addition, standard Debian does not run a RT kernel. So, you might expect some increased latency or other issues. Another thing is that while you can use Debian to make a router, there are already existing linux-based projects for router software (such as
https://dd-wrt.com/ or
http://www.polarcloud.com/tomato) which the community has been optimizing for router use and which usually have things like quality-of-service settings to adjust what thing on your network gets how much of the bandwidth at what time etc. In additiob, the RPi does not have external antennas, so the range is going to be low.
Because there are thousands of RPi-like boards out there, it might make sense to look for one that is more suitable for working as a router and which is known to run these open source linux firmwares. Of couse, a general purpose board like RPI can be more easily repurposed if one day you longer need the set-up that you are building now...
I have no idea what boards to suggest, but maybe start by searching
http://linuxgizmos.com/ or asking on dd-wrt forums