Traditionally you build the concepts you theorize; it's called proof of concept. In any case, let me amend your PROS and CONS list for your current system.

PROS:
- variable and settable health for a bunch of units
- Spells can damage by killing units

CONS:
- Uses up a ridiculous amount of locations (21 per human player, in your example)

- Uses up 2 enemy computers

- Units that leave player ranges lose all damage taken

- Spells can only damage units within the player ranges
- The greater the player 'range' the more potential units that need to be tracked- the smaller the range, the less range spells have and the greater the likelihood of damage resetting

- There is no variable damage, it only detects a unit being killed not by whom or by what.

- vHP system is only for enemies

- Enemies can be team attacked too often for them to do anything (constant death and replace).

- Players are not attributed to their kills and hits; any sort of experience must be a shared team pool.

- Inefficient trigger and location usage

- Can only work on units that are too slow or made too slow to outrun a 1x1 pixel location (2x2 pixel is inherently flawed in that other units can easily steal locations, particularly with how many units you wish it to work for).

I should also note that this method of dealling with excess of 20 units in range is useless:
"Or, if you have spare locations, you can center a location on it, temporarily remove it, and move it back when there are 19 or less zealots in the hero location."
As you may as well us that location to track another enemy rather than pretend it isn't there.

In all, there really isn't any advantage to this system to traditional vHP systems. In fact, the only reason it should ever be used over regular SC fighting mechanics (actual health) is that it supports spells that hurt the units without physically attacking it (and even then it can only do as much damage as every other attack).

Conclusion: Stop spamming the shoutbox

I see several advantages. Do any other VHP systems work for hundreds of units?

Same as every other VHP.

I felt no need to outline VHP for the heroes, as it's been done before.

I haven't got access to Scmdraft for a while, so I haven't been able to test what location size is best. Probably inverted locations.

CONS
If several players attack the same unit, the unit won't die any faster than if only one player attacked it.

Well if you know how to use binary countoffs and single switch randomization, you can rig up a pretty kick ass VHP system with ease.

You could first randomize the hit from one unit to another, and then depending on the amount of the DC that is landed on during randomization, you then divide the base amount of damage from a unit (which you decide the amount of via death counts) by a certain factor with a binary countoff. The resulting quotient could then be the amount of DC's (health) subtracted from the unit being attacked. You could have all this done within a single trigger cycle too. You can also reuse your binary countoffs for all players, to minimize triggering done by the mapper.

Here's an example:

Player 1 tries to hit a Weak Zombie.

Player 1 rolls an attack check with single switch randomization. Let's say the DC parameters for this role are between 0-100. Every increment of DCs (the amount of the increment decided on by the mapper) for this roll will represent a different quality of a successful hit, or even complete miss.

So this means that if the player rolls 0-9 deaths, the hit completely misses. If the player rolls from 10-49 deaths, his base attack amount will be divide by 20. If he rolls from 50-89 deaths, his base attack amount will be divide by 16. If he rolls from 90-100, then his base attack amount will be divided by 14.

Lets say Player 1's unit currently has a base attack damage of 100. He can now inflict either 0 damage (miss), 5 damage, 6 damage, or 7 damage.

You can set up more division amounts if you want, and you can change the base attack amount any way you want for any unit. You can also specify which units are applied to which type of divisions of base attacks.

Then just use a simple system for representing HP with DCs.

But.. If you want to have hordes of zombies, it will get a bit tedious representing VHP for multiple enemies at once. You could try using 1x1 pixel locations constantly being moved over enemies that spawn near the players to employ VHP. You could designate the zergling to represent hit points of a zombie (burrowed), and then cycle through and center locations onto the zerglings every trigger cycle, with use of two different computer types -this way you don't have to mess with giving the actual zombie to different computer players every trigger cycle in order to center locations. Once the locations are set, they should be moved to the zergling that they are currently over as to keep the same locations over their same zombies. From here, you can just have different groups of locations represent different types of zombies; locations 0-9 be weak zombies, 10-19 be normal zombies, 20-29 be strong, etc. Make sure these locations are 1x1 pixel width, so that the locations don't "jump" from one unit to another.

Maybe mix in a couple types of zombies that are always 1 hit kills (so you can have a hordish look to the amounts of enemies without bothering to apply VHP to these 1 hit kill zombies).

Lemme know if any of this was explained poorly.