Practically the only thing entirely correct about the posting. And as "Feminine" is essentially the male version of "Beautiful", Biomancy can do that, too. I can also alter dick size, which makes it a mandatory trait if you want to train sissies, because the game just isn't balanced. It doesn't give you any other option for shrinking that's even 1/100th as reliable. I'm not even sure to this day if Corruption can shrink dicks at all, and good luck (you'll be straight out of luck) getting enough Biomancy assignments.
Biomancy is mandatory because it helps in LOTS of ways, not just to train sissies.
You can take several physical disadvantages (weak, clumsy, etc) for extra points and fix them later, since "fixing" has much better chances than "enhancing".
With Lady Arianna, I never had troubles "fixing" (since she has increased chances).
Shrinking is possible for anything (boobs, asses and cocks), but I think it's balanced by willingness.
If you force a victim, it's more likely to fail, but on really subdued characters it works (or it doesn't works, but there's no drawback as a rebound), so better have a hyp/dom good trainer that can score a crit (thus getting "obedient" instead of submissive) when training someone.
Lady Arianna Fiorentini is indeed a great slaver, but depending on what one wants to do in a playthrough, Kaara de Sindero Oscuro may be better due to her aspect. The other Biomancers are more for RP, though.
Not entirely sure about Kaara's aspect.
I've tried her a couple times, but Lady Arianna is way more efficient in Biomancy, at least in my experience.
Also, there's a quest to recruit Kaara I think, so it's better to get Lady Arianna with Recruiter/ Strong R-A for starters, then find the quest and get Kaara too later.
Whenever I get it, the crit on "Investigate the Depths" does a full gender change on male slavers assigned first, and the second gets a bigger dick, so looks exacatly 0% helpful in creating sissies.
The first is the one that gets fucked, the second it's the fucker, ok.
A male turns into female (and gets slutty), or a female gets a phys boost (and slutty too).
The second gets either a dick enlargement if already has one, or grows a new one if full female.
I'm pretty sure you can train a futanari into a sissy (at least I remember doing it some time ago), so you can assign a female as the 2nd slaver, it'll grow a cock, an then use her/him to get trained (if it's still possible). You can use (for the quest) a slave into slave training, or a dominated/owned slave as second, if you don't want to lose a full slaver.
(note: newly grown cocks are diminutives, around 2-3 inches, so there shouldn't be problems with dick size)
"Quick as You Like" does not let you pick options when sending another slaver. They'll generally wind up slutty and submissive, but not feminine; again, what actually happens is a full gender change if male. So again, exactly 0% useful for creating sissies.
See above.
If there are no options, then you can use the slutty/sub slaver for the steps above (growing a small cock)
No. "Feminine" is a trait, not a stat. Boobs, ass and clothing do affect slave value, though.
Honestly, I'm not sure if it counts or not, I was merely half-guessing.
But there's a quest to capture a tits-loving guy, and give him tits, so it could be a good source of a feminine/beautiful target for sissyfication (which I think it's the one I did. There's also a quest to capture drow males and "punish them", and I think it works similarly)
Tl;DR: Badly unbalanced game at this stage, as Biomancy is the one absolutely essential trait for anyone looking to reliably get slaves past whoremaker fodder value.
You can increase the value of slaves by setting specifics orders.
I usually set it to capture futanari, which tend to have high values.
Then there are quests that give quite OP characters actually, both in value, and utility.
---Capture the Illusionist in Aversol, it's a ridiculous -if dangerous- character. It's a wood elf with M: illusion, read-mind and hypnotic, also has slutty and 3-4 other excellent traits. Lots of value, or an excellent slaver prospect (I think she's around 400-500 value, without training or clothes)
---The cheerleader quest gives you one cheerleader each time it's completed I think, and while I find them useless for anything beyond the cheerleader quest, they do have good value (basically, each time you capture one, their cheerleader aspect stacks)
---The Draki maid is quite common to appear, and while it might take several tries (scum save!) it might end up having tons of value.
---Hold back the Dark gives you a succubus. A bit of a roulette tho, it can be useless or superb value. You can go further and use them in the Green door quest, to give them extra traits, since they're already corrupted.
---You can be a total asshole, and send mediocre slavers into suicide missions on the Deep Mountains.
They "never get seen again" and you lose them, but often they return some time later, with a lot of desirable slave changes/traits (sub, slutty, etc, and even tattoos and slave gear) and a "disliked" rep (which makes them easy prey). I usually do this when the starting slavers suck (since I tend to get lots of good slavers on crit missions later)
---Overall, I don't really have troubles getting valuable slaves. You could even betray the golems (Harmony and Ascendancy Dio'tex -and it's usually better get rid of her-) for some big cash... if you can.