Just buy a left-handed bass. I know music stores rarely stock them, but if you learn to play functionally right handed, (or left handed and upside down if you want to be difficult) you can test out right handed basses to get a feel for them, and then get a lefty of the same brand ordered in, trust me, I spent ages trying to find a decent left-handed bass in stores and it fucking drove me insane.
It never even occurred to me to do what you propose, because I don't hate myself.