Has only happened to me when I deliberately go looking for fetish content disguised as something else, like Bellum Maga (lol).
Bluntly, I don't give a shit if an author inserts (to use the most infamous example from PF's oeuvre that made people shit their pants when it released) some lesbians where one of them used to be a man before getting their dick poofed into a snatch. Their whole tragic backstory arc is entirely optional and you have to actively hammer away at a pretty minimal part of the opening module of Wrath of the Righteous to find this out. It's not like this is some man in a dress trying to shove their girldick down anyone's throat.
Trans person in a fantasy setting using existing magic to change their body to what they want it to be is perfectly fine. It's just taking something from real world and seeing how it would turn out within the rules of the fictional world.
A buddy of mine and I worked out a pretty decent low-magic system based on the Storyteller system, and is in fact loosely based on the Spheres from Ars Magica/Mage. Only instead of Spheres its Words of Power, and you combine somatic and verbal components with a focus of some sort in order to direct and focus your desires. Its worked out pretty well since like Mage/Ars Magica the effects are largely up to the GM/ST... including when things backfire. It also doesn't have Fireballs being thrown around (at least for our chars), so its lead itself to some more inventive, subtle uses of magic There are more ritualistic, safer spells, but they tend to be more utilitarian such as Messenger Swallow (no not Pigeon, because fuck you, Monty Python) that transmits a message or circles of protection and various enchantments. I can share some docs via convo if you'd like.
Ars Magica doesn't lend itself to low power, since even starting mages can fuck up mundanes pretty thoroughly.
Flawless Magic+Cautious Sorcerer means you don't roll any botch dice on your formulaic spells unless you cast in level 5 or higher hostile aura. And not even most churches have Divine 5 except for maybe at the altar.
If you're willing to play more risky, replace Flawless Magic with Flexible Formulaic Magic and enjoy needing 10 less Lab Total to invent spells in one season or just upgrade all your Voice range spells to Sight range.
And just limiting things to spells level 15 or under from the core:
Agony of the Beast/Circle of Beast Warding fucks up anyone mounted.
Disguise of the New Visage is sufficient enough disguise to fool anyone.
The Wound That Weeps only inflicts a Light Wound, but if you stack it with Multicast Mastery, it's brutal.
Flexible Magic lets you do a lot of trolling with Lifting the Dangling Puppet and making it Diameter or Sun duration.
Trap of the Entwining Vines is Hold Person except it lasts until sunset/sunrise.
Shriek of the Impeding Shafts is immunity to missiles fired from more than 10 yards away and huge bonus against missiles fired from closer range (+9 in a system that uses d10 roll).
Pass the Unyielding Portal: No wooden door will ever keep you out.
Piercing Shaft of Wood is low damage, but easy to cast when sitting in a tree.
You can give Dance of the Staves a duration to have some free damage you don't need to control.
Transformation of the Thorny Staff+Tangle of Wood and Thorns is a single target Hold that does damage.
Forcelessly casting Blade of the Virulent Flame on enemy weapon and making it resistable with Parma. (Either by Fast-cast or Flexible)
Flash of the Scarlet Flame is Blindness that can be permanent if the target botches its roll.
Hornet Fire makes everyone roll extra botch dice and Flexible turns it into Diam duration.
Prying Eyes is perfect spying spell.
Disguise of Transformed Image is a component to perfect disguise.
Veil of Invisibility is level 20, but you can make it level 15 by making it Personal range instead of Touch.
Wizard's Sidestep: Immunity to first hit in combat and +9 to Defense afterwards. Use Flexible magic to buff all your henchmen with it.
Calm the Motion of the Heart: Erase a single emotion from the target until they have a chance to feel it again.
Loss of but a Moment's Memory: Mindwipe.
Call to Slumber: Instant Sleep with no way to resist. Can be made Sight range with flexible.
Crystal Dart is a low level damage staple.
Fist of Shattering: Bye bye, walls.
Rusted Decay of Ten-Score Years: Bye bye, metal weapons.
Trackless Step: self-explanatory
Hands of Grasping Earth: Another Hold spell.
And that's just spells from the Corebook. Transforming Mythic Europe, Hermetic Projects and Magi of Hermes has spells that are just as good or better. IIRC, you can get an okay teleport with level 15.