Few underused fetishes for a title like this could be:
Size Differences/Big Monsters are their Genitialia
Impregnation/Pregnancy of varied sizes and maybe Egg Laying/Oviposition
Inflation. Cum, Eggs, liquids and otherwise.
Mutated/Corrupted beasts, insects and creatures? To somewhat horror level and much bigger sizes? I dunno. Just a fresh idea.
I am assuming "Transformations" means Character body sizes, yours or others changes. Such as for "Breeding" purposes?
Just some ideas i thought would maybe fit this. These things would probably take a lot of time. And everything should more or less be consquences for not avoiding...if you didn't want to end up some monsters toy or intentionally did it.
If you are gonna have Game Overs, at least make decent room in between areas for "Bonfires", as to not piss off people from progress too much. Just a fair suggestion.
I can't come up with anything else for now. If i do, i'll let you know. Machines and Forniphilia isn't exactly my thing, but hey, something for someone else, i guess.