You can easily set up your theremin to be a "leftie" (i.e. pitch on the left, volume on the right) but this is something only left-handed people find advantageous. The two most celebrated thereminists of the decades following the invention of the theremin (Clara Rockmore and Samuel Hoffman) were both professional violinists, and both played the theremin in what is now considered the "traditional" configuration, with the rod on the right and the loop on the left. Lev Termen himself, the inventor of the instrument, was a cellist who bowed with the right hand as all cellists do.
So why isn't the theremin configured for pitch control by the left hand, the way it is on all fingerboard instruments - violins, cellos, basses, lutes, guitars, etc. etc.?
It is delegated to the right hand (in right-handed thereminists) because that is the hand with the greatest dexterity. The early thereminists experimented endlessly with all possibilities and it was unanimously decided that the traditional theremin configuration was the best and most efficient one for the instrument.
Be all that as it may, it has not stopped each successive generation of thereminists from experimenting with exactly what you are proposing. Most of them do it unaware that it has all been done before and, for various reasons, ultimately rejected.
Another thing that has been endlessly experimented with is reversing the action of the volume antenna - modifying the response so that volume gets louder as the hand approaches the loop and softer as it withdraws.
Experiment all you like, but you should be aware that many others before you, with the same knowledge and background as yourself, have been there & done that and ultimately decided against what you are proposing.