Also, to me the webshooters are more fantastic than the natural ability Peter developed after his rebirth. I found it ridiculous that after pressing his webshooter Peter was able to produce vast amounts of webbing from tiny looking cartridges.
It's not that different from the silly-string principle, a pressurized fluid that expands when dispensed. That's not the implausible part. The implausible part is the idea of a strand of really, really lightweight webbing being fired hundreds of feet through the air. The air resistance would slow it to a stop just a few feet from the nozzle at most. Spiders don't shoot webbing over distances, they attach it directly to an anchor point and then crawl or leap to the next one, reeling it out behind them.
But it is the Marvel Universe, after all, so realistic physics isn't exactly a priority. The webshooters are cool gadgets and I enjoyed writing about their workings. Plus I was able to make good use of the spare webfluid cartridges in a couple of unconventional ways, though that certainly has plenty of precedent in the comics. There's so much you can do with the webshooters in storytelling terms that you just can't do with built-in spinnerets.
I don`t think it would look very good if Peter would spit webbing from his mouth and it certainly wouldn`t work from his bottom. Therefore the wrists are the logical choice.
From a storytelling perspective, of course. But what's the in-universe, biological explanation? Hmm, well, to be fair, spiders' spinnerets are actually a sort of extra set of miniature limbs, so maybe there is some slight correspondence. Still, it's a reach.
Also, the comics never actually made any use of the organic webshooters. There was one storyline that introduced them, but nothing thereafter followed up on them, and although the stories no longer explicitly featured his webshooters, neither was it explicit that they were absent. And the whole cocoon/transformation thing he went through in
Disassembled was pretty much ignored when they turned around and put him through
another, remarkably similar transformation in
The Other. In the first transformation, Paul Jenkins gave him an enhanced spider-sense that somehow included the ability to communicate with insects (which is odd, since spiders are arachnids), and then it was never mentioned again, and then
The Other gave him what was supposedly another enhancement of his spider-sense, which basically gave him senses like those of spiders (pretty much how I interpreted his normal spider-sense in
Drowned in Thunder, ironically). And that, too, was never mentioned again after that storyline, because they then got sidetracked into the whole Iron Spider/Civil War/unmasking/Aunt May shooting/black costume/One More Mess business, and then they rebooted the whole thing so he was back to his ordinary powers again. There have been so many changes in the past few years that no storyline or idea has gotten any real follow-through. I was happy to set my novel before all those changes happened, where it was still basically the familiar state of affairs except for the changes that JMS had introduced in a more gradual, natural way (Peter becoming a teacher, Aunt May finding out, MJ going into theater work).