I realize that yes, Venom's coming out of the Sony end of this "okay, we'll share universes, sort of" deal, not Marvel Studios. The Spiderman deal came through after a lot of Civil War had already been structured (hence their choice to make it just about government sponsorship instead of the whole secret identity), but he had played a big (different) role in the original Civil War. Introducing him that way let them skip a lot of backstory that people have already seen in various failed reboots, but also let them inject one of those great nods to the comics.

Well, in the comics during my youth as I remember them, the symbiote is first introduced on Earth with Spiderman (following some space adventures). After he realizes he's been running around town in his sleep, who does he turn to for help with the thing? The Fantastic Four. Reed Richards figures out how to use sonic waves to separate the symbiote from Peter. And, since he had been using the 'suit' that is the symbiote, he finds himself without any street clothes, and heads back home in a F4 jumpsuit with a paper bag over his head (which makes some minor news about who this new mystery member of the 4 is when he of course encounters and foils some generic hooligan baddies on the way in his jumpsuit & paper bag uniform).

Previews for Venom looks like they're not intending to tie in MCU Spiderman in any way, but this seems like a perfect opportunity for them to do for F4 what they did with Spiderman in-reverse.

Probably won't happen, Venom is probably done with principal photography, Sony may not care, Marvel may not be ready nor want to associate them this way for their first appearance, and the Spiderman-less symbiote plot might not even have an opportune place to inject this, but figured I'd throw the idea out there.