Back to OP's question. You can give Mica a call/Email and I'm sure alembic can provide a modification for you to install for a switch or dimmer. It would most likely mean another hole somewhere on that lovely body though.
Mine was done as an later modification and as it has the jack and 5 pin socket mounted on the lower edge my dimmer control is where the 5 pin socket is on your bass.
I'm sure something can be done.

On the other hand, the penalty for poking a hole in a Dragon's uhhhh... hiney, might be severe. 🐲

Thanks.  Not interested in modifying the bass.

Did you check and see if there is a dimmer inside the electronics cavity? Just a little blue trimpot in all likelihood.