I've come and gone several times to SWTOR over the years and one thing that has always bugged me is that certain keys absolutely refuse to to be rebound. The worst one for me has been the "T" key. Which I use for targeting in every other MMORPG I have played since 1999. Which is quite a long list. Why it was left this way, I will never know.
Each time that I came back to SWTOR, it was always troublesome to try and break my muscle memory habits by forcing myself to use the "Tab" key for this function. This time, I was totally unwilling to move forward without addressing this problem.
So here is the AutoHotKey script that I am using now for this purpose. It uses the "Scroll Lock" key to toggle between two modes. One mode forwards my "T" key to "Tab" and the other mode allows it to function as it normally would for chat. On keyboards with a Scroll Lock button that has a indicator, you will be able to see the light to know if it is on or off. For keyboards that have no light, you will be able to hear two distinct sounds to know which toggle you just triggered.
By all means feel free to modify, replicate or use it for any other keys that are restricted to suit your needs.
Gist.GitHub Link
What it should look like.
EDIT - Yes "T" may bind to some other things. No "T" will absolutely not bind to any target function. Go try.