Multiple outlets w/bottom switched from two switch locations
Your diagram would look something like this if installed in conduit. I'm just trying to show the wiring and not any cable configurations. The yellow wires are your travelers which are needed for a 3 way switch. The links on the outlets need to be removed on the hot side. The hot and neutral are run to the last switch because the OP stated there will be more outlets. In my humble opinion, conduit would be your best bet. Some of the real experts will chime in.