I figured out the way vision works a while back. It turns out every 100 frames, vision updates. If you leave a unit with shared vision over this frame, you get to keep vision. This resolves the "flicker" effect when you constantly create/remove a unit by the player who does not have vision with himself.
Essentially what happens, you can set view range to:
Hydralisk: 6
Zergling: 5
Drone: 7
Defiler: 10
Hunter Killer: 8
Ghost: 11 (maybe?)
Infested Kerrigan: 9 (maybe?)
Spider Mine: 3 (maybe?)
Blinded unit: don't know, 1? doesn't matter much anyway.
Now, the maybes are due to when created, I'm not sure if they go through their cloak routine. To keep things pretty, we don't want to see a cloaked unit cloaking every time it is created. The burrowed zerg units work flawlessly, however. The basic premise is this:
When the player moves (center 1 px/inverted location), create the vision unit (5=zergling) with the burrow property, then immediately remove it. This is the first step. If you just do this, you will lose vision when you stand still. Next, you need a counter which counts the frames, and on every 100th frame, create a vision unit, wait until the next trigger cycle, then remove it. This will carry the vision over the vision reset frame, leaving you with vision even if you stand still.
An important note: Giving units DOES NOT update vision. Creating units DOES update vision. The only time giving units updates vision is if you control that unit over the vision reset frame (which we can exploit in this method). Also, if any unit is blinded, this resets the vision update frame to that instant the unit is blinded, effectively crippling this system, since there's no way to know which frame the unit was blinded on. In other words, you can't use optical flare without vigorous testing.
If this sounds appealing, I'll link you to my test map so you can see it in action.
"Parliamentary inquiry, Mr. Chairman - do we have to call the Gentleman a gentleman if he's not one?"