Actually missed a line, regenerateslave() does re-generate the class with the chosen race, age, and sex. so your method of testing *should* be valid for those 3, but it will still be using random hair, skin, tits, and ass for generation, not what you choose. With 0.5 you can confirm this by turning on debug mode.
However 0.5.18c is completely broken for me. It broke my 0.5.18b save to make it think main quest was done. Starting a new game gives you every single unique character in the game at the start, which is a tad broken. looking at the code... it's Mansion.gd line 43, should be debug == true.