Anyone stuck at "installing game client 0%" the easy fix is to force quit the launcher from task manager, then navigate to the SWTOR install directory and delete the following:
swtor (just the client folder, not the entire install!!!)
and any stale game client patch folders like
that will force the launcher to download "Game Client 1" and then patch directly to "Game Client 82" or whatever it's on.
I have to do this every time on all 3 of my swtor comps, it's a PITA but it works.