Adding network switch
 

I'm looking to upgrade my router but I'm running into space issues. I have a built-in box that holds all my wired network connections and I don't think my new router will fit in it. So I was thinking about adding a switch inside the box for my wired connections and then just plugging router into the switch and placing it outside the box. Any reason why I won't want to run this way?

That would work fine. In fact, if it's a wireless router, it should work better outside of a box. For best LAN performance, get a Gigabit switch.