Could The Pokémon Company print an exact replica of 1st Edition Base Set Charizard if they absolutely had to?
What do you think would be the hardest characteristic to get right? They definitely have access to high res images of base set but could they replicate the holo pattern, the card stock, and the 1st edition stamp perfectly? Could they make a card that would pass Spot-Fluorescent light analysis?
Perhaps the hardest issue is a legal one
Even if they could 1 to 1 the art, the card stock is not the same for modern pokemon cards, especially 1st Edition Base. I don’t know if they could successfully replicate the more matte style of 1st Edition base set cards. They also feel slightly heftier than modern pokemon cards.
I think you were getting at a thought exercise, so, I’ll imagine this question was asked:
“Could WotC today print an exact replica of the Base First Zard (or other card), legal issues aside? What would the biggest challenge be?”
I’d have to say the card stock would be hard to match. Yeah. but there is some variance there… Also, the foil might be tough to replicate, since both the original holo pattern and exact foil material is not used presently, and might not even exist anymore - as previously mentioned, heftier, and a different material than modern cards.
And then of course, remember it IS modern WotC, so they would definitely find a way to screw it up. 
As others have already mentioned, the difficulty of perfectly replicating a 30 year old card sort of nullifies the question. Even if they use the same design file, the paper would not be exactly the same, the ink would not be exactly the same, something would be different that would give it away. Just look at how much variation there is in the early Base-Fossil era already where two cards in the same set of the same type can be completely different colors because of differences in the print run.
Even in a hypothetical scenario where they attempted to get it as close as possible to produce an exact match, it would be different and you’d be able to tell. The ability to distinguish between them would prevent them from being seen or treated like the same card. It would be just like it is today where the card has been reprinted various times but none are viewed as interchangeable. That would be true here no matter how close they got it.
But furthermore, the big thing that would give it away is obviously copyright. In addition to having to remove the WotC copyright, they’d also have to update the date. There is no getting around that detail and so a perfect recreation in every other way still stops at the copyright. It would be a visually different card and be treated like one.
Ignoring any legal issue, the next hardest step is probably getting the correct holo cardstock. It’s a proprietary pattern, so you would have to get the other company to agree to reporduce and sell it to you and there’s a lot of question marks about whether they can or would
They could, but it would be a pain in the ass. They would just hop in with their supplier to check all the properties of the material, then mimic all of it. It would take a while, and there would be no point.
I work in printing on different canvas materials, so I felt confident to comment 