Feel like adding to the general conversation here. I don’t particularly love size content featuring real people. I have fantasized about celebrities of course- I think that’s a pretty natural thing for people to do- but using their likeness in sexual content just doesn’t feel comfortable for me. Not arguing that there’s anything morally wrong with it since the careers of actors/models/etc are based around their image, but it feels uncomfortable imagining myself in that scenario. If someone thought I was that attractive I might even be flattered, but it would be very weird to actually see myself in kink-based content.
And of course that gets into even more grey area. Like creating sexualized content of a fictional character played by a real person: does that feel strange to me? I don’t know. And I’ve definitely been inspired by celebrities’ looks and personalities for characters I’ve created.
Not trying to be a moral grandstander or anything! I’m not arguing that any of this is unethical. This is just purely what I’m comfortable with. Though I imagine going into this industry there’s an understanding that people are going to find you beautiful. 
I do LOVE fanfiction, though it can definitely range from great to terrible. I struggle to enjoy it when the character acts completely different from their canon personality, but a well written story about how they would react in a size-based scenario is fantastic.
All this talk about Henry Cavill, though. With him working on the Warhammer 40k series we might have plenty of size content to look forward to. A lot of the more powerful characters in that series can range from 8-15 feet tall. I know characters can manipulate their size to be hundreds of feet tall as well. Very exciting!