A Passive Cooldownable Spell - AKA my Nemesis

I must admit it, my nemesis is to create a passive cooldownable spell (such as Reincarnation, but I can't use it because it only fires when a unit dies).
I tried all the following things to create such ability:

1. Using the orb of slow ability (CONS: it is an orb and it shows a very horrible disabled icon);
2. Using Reincarnation (CONS: very tricky to handle with if a unit has already reincarnation, moreover when a unit dies it is unselected, untargeted and the hero's icon on the left side of the screen becomes black for a while);
3. Using an active ability such as Berserk with a passive icon and ordering to a hero to use it when needed (not a very bad idea but -> CONS: as I write on one of my last posts, it stops the unit's current movements and orders, seems that I can't workaround this, even if I store the unit's current orders.).

I would really appreciate any help cause this is really my nemesis
Thanks.

I would use a passive ability and trigger the whole effect, sounds like the easiest solution to me, the obvious disadvantage is that it won't show the cooldown effect on the icon

Yes, sigh :(
I already have many abilities completely triggered with timers like your solution but I wanted to show the cooldown effect...
Do you know Vexorian a way to issue a order without interrupting a unit's current orders? Thanks.

You could just replace the ability with one that has a darkened icon, it won't show the cycle animation but it is much better than nothing.

Cause the answer to your last question is nope

Well, that's not bad!!! It can be a nice compromise! REP added! Thank you so much!

How about making a dummy spell with the same icon and the cooldown you want; then just add the dummy spell to the hero and have him use it to show the cooldown. After that, remove the dummy spell after the cooldown has happened.

Your solution is similar to my point 3 in the first post, the problem is that a unit stops its current actions/orders if you issue it to use any ability and this is not good. Thanks.

Not quite what I meant. I meant that as a solution to the "not showing a cooldown" part if you trigger the whole ability as Vexorian suggested.

If you base the ability off of something you know doesn't interrupt orders (summons don't, as far as I remember) and show that during the time the ability should be 'cooling down', then I think you'll be set.

How about using the 'swap out ability thing', but use the spell block item ability (the one that blocks a spell targeted at the unit) and create a dummy unit to cast a spell on the hero, putting the ability into cooldown.

So you have another ability most of the time, until the passive is triggered, at which time you swap it for the spell block, create a dummy which triggers the spell block and then you swap back to the other passive after cooldown finishes.

Uhm, can you explain better plz? What do you mean by "summons don't"? I tested many abilities like Wind Walk, Berserk, Mana Shield, Immolation etc... and all of them interrupt a unit's movement if ordered by triggers. Should I use something like feral wolves? Thanks.

Omg, another VERY GOOD IDEA! Rep added of course! Just a thing: spell shield is an active (not passive as I thought) ability and this is better because i can detect when a unit uses it, even if it actually doesn't "use" it (because it automatically blocks a spell casted)! Thanks!!!