Most rulesets state that zombies can be stunned, sic. "by blasting them with a dart blaster or throwing a sock at them". Depending on how your moderator team has written and interprets their ruleset...
I suspect that most rulesets don't explicitly define the term "blaster", and this word is generally taken to refer to anything which flings a dart, which includes homemade contraptions. Nobody said that a "blaster" has to be in someone's hands when it fires...
Such rules-lawyering is ultimately moot IMHO. Any competent mod squad will decide whether to allow mines depending on the perceived level of risk, the potential to create conflicts, and how much they add to a game. I think that these mines can be made very safely, won't create conflicts so long as zombies aren't cheating spoilsports (and if they are then mines are the least of your problems), and they can add an interesting dimension to gameplay in some situations, such as point-defense missions. This is the argument that you might need to present to your moderators.
There are easy tactics that will deal with mines, to be sure, but those depend on all of the zombies being informed as to the presence of, well, nerf mines and tripwires.
. . . or on noticing the mines and tripwires, or knowing that there are mines around because they already tripped one. Given that the horde will quickly find out about the presence of mines, we need to make sure that they will hinder the horde even if the horde knows about them, such as:
. . . set[ing] up a bunch of these mines around your play area, then watch as the zombies learn to watch their feet and not their heads.
This is a really good idea, assuming that the zombies are good sports.
The low launch angle of my current designs makes placing them under trees feasible, and they could be painted black and loaded with darkly coloured darts. If thin darkly coloured thread were to be used, and especially if the mines were to be deployed at night, they could be very
hard to find. So long as the horde does not know where each and every mine is, they will need to move with caution, which reduces both their attentiveness and responsiveness to human actions.
On the other hand, if zombies aren't good sports, then this is where their ability to ignore stuns when there are no humans to call them out on it will be especially problematic.
But on the other hand, this would be extremely useful in hold type missions. [...] All you need is a ghost-type soldier to refill them secretly.
In a hold, there tends to be a lull after a charge with a duration equal to the zombie's stun timers - and a charge is when the mines are the most likely to be triggered. Given that the zombies will know where each mine is after it is triggered once, I see the primary value of mines as lying not in surprise but in nuisance. The zombies won't be able to leisurely disable or avoid the mines even if they already know where they all are because, when they reach the mines, they will be in range and under fire. Overall, I don't see the need for a ghost-type here. If someone does want to be sneaky, they would do better to reload and reposition the hidden mines which are distributed throughout the campus.