Probably not. It's a pretty simple install, and since different players are going to want them in different positions it probably wouldn't be advantageous to sell them pre-installed on a pickguard.
I used to own a bass with a thumb rest, but I took it off! In my early days of bass playing (just 4 years ago actually) I was leaving my thumb on there all the time and not muting. I took it off, started to mute much better and have never missed it since.
I also removed mine from a non EB bass i had a few years ago, found that it was just getting in the way and i was tripping over it all the time. But if you feel the need for one there easly avalible to buy an install, just not a nice thought of drilling holes in the body unless you can get on that fastens from the rear of the P,G so all that needs drilling is the P,G and can be replaced if you decide that you want to remove it later on with out leaving holes behind. (.....horrible thought.....)