I tried v3 and walked away for this very reason. V4 peek is a step in the right direction - but I'm not quite comfortable with Windows-space_bar - and having to HOLD it. Meaning it takes BOTH hands to launch an app.
Trying to think of ways to have the fences come into view without having to physically HOLD them in view with my finger.
* Double click desktop already toggles hide/show. Maybe an option to EITHER hide/show OR bring-to-front and hold.
* Double click taskbar brings them all to front
* Moving to a hot corner brings them to front. Of course it's easy to accidently do that. So they'd only be in front for 2 seconds OR as long as the pointer was inside any fence. After 2 seconds of not being inside a fence, send to back.