It certainly isn't conventional, but if it works for you I would say 'just go with the flow'. I have a similar technique.
There have been dozens of guitar heroes with unconventional playing styles and setups (Jeff Beck springs immediately to mind), but it just makes you be more individual and creative in comparison to everyone else. Some things may be easier to play with that style, some not. Unless it starts to hurt in the base of your thumb.. then you may need to do physio and start 'correcting' the technique.
For myself, I anchor the palm of my hand on the bridge and my pinky on the scratchplate. I can't do the floating tremolo picking of people like Steve Vai, I have very limited movement and do use the thumb a lot more than most, almost extending and arching it with the picking up and down respectively, just like you do, but mine does come slightly more from the wrist rather than the thumb.