If everyone can make sysops, then a vandal with a handful of sockpuppets can do constant vandalism, always resysoping any of his accounts that are desysopped.
If everyone can edit pages, then a vandal with a handful of sockpuppets can do constant vandalism, always reinstating any of his edits that are reverted. Nice, you're refuting yourself :-)
Nonsense. We handle vandals with multiple accounts all the time. It just requires multiple blocks. He'd have to have a very large number of sockpuppets to get around them, and an easy way to change IP address frequently to avoid being stopped by autoblock. If he tries to edit anonymously, or create new accounts, we can semi-protect the page. There are all kinds of things we can do, but only because admins have powers that vandals don't. If you remove that advantage, then vandals can pretty much do what they like.