What does Apple consider to be tethering?
Apple implements tethering, so if your app proxies TCP/IP traffic directly, you will probably run afoul of several aspects of the review process.

Clearly, if your app is doing things to add value to the network you'll likely have more legs to stand on that your app isn't just the same implementation as carrier tethering:


linking IOT type devices
speak protocols other than just TCP/IP
allow filtering, reporting, proxy, QOS controls


Like all app submissions, your milage may vary. You can do the work and take your chances or you can line up a big customer and sell the app B2B style if you are worried about Apple deciding to pass on your app.