Vocal cord surgery eh? A quick web search suggestes somethjng like this will set you back $5k. The thing is, the effectiveness seems to be dependent on the age of the patient. Younger people tend to have better results.
I'm not one to tell Frank how to spend his money, but at this point, it's like beating a dead horse. No amount of voice changing, forehead reduction, or gut cinchig is going to convince anyone that the giant, horse-like man they are talking to is in fact a woman. When you factor in all the ongoing investment that will be needed just to simply maintain Johns current baseline gashtly appearance, it's really hard to envision any kind of ROI, even when it is measured purely in the currency of Franks fucked up fetishes. I understand he is a man of means, but he really should cut his losses. In a few years he is going to have to spend money to rework the boobs, patch up bald spots, or roatate whatever friction components make up Johns false vagina.