You have edited the post. Previously you have been suggesting that speech is naturally attached to convincing slaves into submission, rather than terrorizing them. Totally absurd.
Yes, speech requirement to get a professions is a good idea, also a good way of balancing, but totally different than one suggested by you before.
Having such requirements (high speech to convince slavers leader to honor you with guilds membership), you couldn't create a power build AND be a slaver with army of drones (don't use word "bot" for slaves, thats something quite different).
I'm not starting any flame war, just opposing absurds.
The idea you derived from my suggestion (few posts above) would indeed balance the game, and wouldn't be as awkward as your original. So now I can say I agree - to some point.
Add the requirement for shackles, cages, collars, cuffs etc (you would need lock-picking, some science or simply cash to buy them), outdoorsman skill requirement to herd them safely trough wasteland (failed test - you lost a slave, either he managed to run away, or died)... Than calculate all to make sure, that creation of a playable slave is possible, yet it couldn't be a power build at the same time.
Logic + balance.
Hope you agree.