There's a way of doing overlays - SublimeLines does that. I find it less user friendly, since that does not respect font and theme settings and would require user to create images (via some script ofc) for the theme and font they use.
What do you mean by syntatic destruction?
What it does is add and then remove regions - it doesn't mess with the syntax file you've selected.
Edit: acutally, you can do overlays only on gutter, so you are right that it's not possible.