I am tired of the look of my swamp ash body on my bass. Leland Sylar carved his bass.
Here is an article where he says that when he carved it it put it out a balance and he added a weight to balance the body and head stock. Why Lee Sklar hand-carved his pre-CBS Fender | Guitar World
I would also like the change the colour of it too.
Is there anything to consider before I start taking the chisels and wood stain to my bass?
I guess I would ask if you are already a woodcarver and are confident in your skills here 
I am sure you realize that this will likely destroy the resale value of the bass.
If you’re cool with that then go for it!
Consider the weight and balance. You’ll be taking mass away from the body, but not the neck. Sklar threw that bass way out of balance because he chopped off the upper horn and shifted the strap point.
It would seem he’s still using it though!
If you are good with wood and your hands (wait what?) anyways, 
You can. Shaping the body is easy enough just a little at a time, smoothing is pretty easy too, for me it’s the paint prep, with grain fill and even coating and the wait in between.
