This may be a Don Quixote level endeavour, but I’ve been thinking about increasing my pornstar options and my general level of depravity by hiring pornstars, including noobs, to shoot videos for a website that doesn’t (and won’t) exist. Given all of the options open to a porn producer, versus a regular hobbiest, the kinds of play possible are endless.  

I assume you intend to book "the talent" through the agencies that they work.  What do you intend to tell them when they ask you what you've produced to date?  You realize the girls are repped by these agencies as much to find them legitimate work with established porn producers as they are to protect them from situations like this? What agency would send a girl to you unless you had some prior production experience....or at a minimum an active porn website?

I'm not necessarily looking for "top talent". Rather, I'm looking for fresh talent that's willing to put in some effort in the (erroneous) hope that this will be their big break.  

Isn't it much easier to tell them the truth and ask if they would allow filming the encounter, if the price is right? Role play included, of course, as I see. I've read that some Porn Stars allow it for an extra and higher cost. They sometimes ask for a copy of the material, in case you publish it, perhaps, because I, if I were you, would keep it for myself. Yeah, don't even think about publishing it without her express consent.

For this to be a legal porn shoot (and not P4P), I think you would need consent forms: model release, 2257 certification, record retention, ...  Depending on the jurisdiction, shooting porn may or may not be legal. In the LA area, they have the new (new? a few years old)  law that requires the use of condoms for non-oral insertion. Most legit porn companies also require sequential recent blood tests to prove that you are healthy. And I'm not talking about your cholesterol level.    
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Other than that, I like the idea!  Need a camera man?

Some less intelligent hot chicks might be lured into doing fly by night porn, but they won't be anyone that you know from actual porn. I'm sure all those casting videos with anyone you've heard of had age verification, blood tests, etc., has people have mentioned above.  
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And if you are scamming these girls about the nature of the operation (understand you intend to pay them the going rate), word would probably get around.
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Also, it's not the kind of thing I would want to try to write off on my taxes. "Yes, Mr. IRS agent, I've kept all the receipts from my shady fake porn business."

The condom law applies only to Los Angeles County. Word has it that AHF's Michael Weinstein had something to gain from it financially, so he pulled his political strings to somehow get the measure passed. He tried to make it statewide in the following election but thankfully the voters said no. They've only recently begun "enforcing" this condom law, which requires the producer to pay $1600 to the county health department along with proof that performers have received county-approved training on blood-born pathogens. And that's of course if he doesn't plan on using a condom. However, this, 2257 and any other legal matter regarding production apply only to videos that are publicly released, which OP doesn't seem intent on doing with his. If he does plan to release it publicly, then he should get tested at a facility recognized by the industry, designate a custodian of records with a physical address, and perhaps shoot outside LA County to avoid the Measure B nonsense.

Good points and details I didn't know (the public release stuff).

Oh no, home tests definitely won't be acceptable. Industry folks know what to look for and where to look, specifically the Free Speech Coalition's PASS database where performers and their statuses are listed. I believe the tests have to be done within a 14-day window to be considered current. Full-panel tests include both blood (HIV, Hep B, Syphilis) and urine (chlamydia and gonorrhea).

without a history you wont get any top notch talent and agencies wont deal with you .

I totally agree with Kitty. The laws involved with running a legit porn company are complicated and not to be taken lightly. I wouldn't go any further without talking to a lawyer.