Yes, you can certainly use layers to store a T-Pose so you can go back to sculpt. I plan to try to use that in the future, but I don’t think I’ve done it how you are.
The one I’ve used a lot is this: I store a Morph at the lowest division. Then I pose things. Then when I go back to my low division I hit the [SWITCH] button to flash back and forth. Then move the division slider back up. I’ve done that for quite a few things, especially organic.
To be honest about this character though is i believe I posed him and kept it permanent! I just took him really far in the T-pose version first. The concept is almost in a T-Pose to begin with. Then once things were pretty solid I moved everything into place and then started to sclupt back into it. I really wish I could have kept that T-Pose like you are saying. That would have been great at least on the waist down (legs).