and in re to organic webbing, personally, I've always felt organic webbing makes the most sense in context of the symbiote suits. It's not the person himself developing special glands in his wrists/forearms, but the organic suit itself that develops and fires off the webbing/tendrils. So, theoretically, you could fire the webbing/tendrils from any part of the suit, not just the hands ( just like Venom and Carnage do ).
I've always thought that one way to "ground in realism" the whole symbiote suit is to go the Ultimate direction, and make the suit a product of the lab, not an alien life form.
The project could be based on using some kind of virus and genetically enhanced spider silk/webbing to create an "organic" suit that conforms to the user's body. Instead of soldiers having to wear heavy armor, or giving them bulky exoskeleton/robot armor (Iron Man), you create a lightweight, compact, skin tight suit that offers enormous protection ( spider silk is supposed to be strong, after all ).
taking it a step further, just like in the Ultimate storyline, the suit is also designed to "bond" to the host's DNA and improve all of his physical abilities. So, enhanced strength, speed, reflexes, healing, etc.
and because the suit is bonded to the host's DNA, he can control it with his mind ( just like Venom and Carnage ). So, you can command it to cover you body, or retract into a central location ( base of neck, perhaps ), etc.