It's certainly possible to conceive of contractual arrangements that would allow for this, but prosecutors could equally well argue that such arrangements were a mere instrumentality to facilitate otherwise illegal activity, and that argument would rest upon the net direction of economic activity.

Suppose Alice is willing to have sex with Bob for $100, and Carol owns a video camera and operates a porn website. So if Carol pays Alice $100 and films and publishes her having sex with Bob, then fair enough, Alice is a porn actress. But in this context, Bob is also someone who would be willing to pay $100 to have sex with Alice, were it not illegal to do so. If Bob offers $100 to Carol, who gives it to Alice, then Charlie is engaged in an illegal pimping relationship with Alice. Carol could pay Bob $100, in which case Bob would also be an actor, but this doesn't make any economic sense for Carol because it's unlikely that every sexual transaction is going to generate $200 of viewing revenue. I mean, why would anyone watch porn if you could just go over to Carol's and make porn, and walk out with more money than you came in with? OK, Carol could pay bob only $10 because of supply and demand, but that still doesn't make sense for Charlie, who's operating at a loss.

In reality, the economic motivator is Alice's willingness to have sex for $100 and Bob's willingness to pay for her participation. We could introduce Don, who holds himself out as a booking agent of some sort, and accepts some sort of 'membership fee' from Bob before going on to set up a porn shoot over at Carol's house, but that's just the same situation with an extra helping of conspiracy on the side, plus the economic incentives make even less sense. When you get right down to it the reality is that nobody particularly wants to pay Bob for sex (at least not in the short term) and Bob is in any case more interested in having sex than getting paid. His sexual drive is the motivating factor for any transaction; if no men wanted to have sex, Alice might be able to make $100 by, I dunno, selling hamburgers, but it's unlikely that Bob could consider $100 worth of hamburgers an adequate substitute for having sex with Alice.

Of course the other problem with this is that many people who patronize prostitutes wouldn't necessarily want to appear in sex videos on porn-not-prostitution.com, although I suppose you could get around that by having all the videos in silhouette or pixelating the images enough to obscure the participants' identities or something.

It's not impossible to come up with some legal scheme whereby Bob sets himself up as a porn producer and is the star of the movies he directs and produces, but I think it would still be almost impossible to generalize this out to some sort of platform. Courts would draw a distinction between Bob actively working a producer of pornography and running a business like Hugh Hefner or whoever, vs 'Carols Adult Video Services' whose clientele consisted entirely of loss-making 'adult video producers' who engaged in no commercial activity whatsoever other participation in sex acts.

Going back to hamburgers, you probably wouldn't be able to get out of restaurant licensing/inspection/etc. requirements by claiming that all the people sitting at tables eating hamburgers were actually trainee food-tasters in a school for culinary critics, not a restaurant, nosiree.