My customers would rather pay me to over build than to one day find a hole in it. Besides more often than not I do what I'm satisfied with not the HO and I can sleep at night.Using the logic of "well its going to be kicked" you may as well tear out all the framing and put block in there.
For this application, a good quality thin set will work fine. Sure a porcelain or hard ceramic tile would be best but even a lightweight 6x6 will do just fine. Its a home and a dry area. Over constructing something to avoid abuse is wasteful. If a foot goes through it, that would take significant force and a contractor is not responsible for abuse. No matter how durable you build it, it could be broken under abusive situations. Don't over build and charge extra to do it. You think that makes a HO happy?