Rather than being identical to guardian angel's effect, it should play the death animation at descending speed, then play the animation in reverse at ascending speed until the player is upright again. Add some fancy-shmancy (and UNIQUE) particles as needed.
there also needs to be a duck sound at the end
Imagine Zed'd revive..
like kalista black spear??
I love this idea, but it probably takes a lot of work to code or whatever for all the champions and skins with different death animations. But I could be wrong, i have no idea how much work it takes lol. But I don't see Riot doing this any time soon unfortunately.
I can think of 3 problems.
Yes please
That'd look hella buggy with some champs/skins and wouldn't be good for consistency. If I'm in the middle of a fight and someone's going to revive, I want to see that white swirl to know right away what's going not, and not have to recognize "Oh, this is X skin's unique death animation being played at a weird speed."
Huh, I thought it did this already, guess I don't pay attention to my revival when there's 9 people killing each other around me.
make dragonslayer rengar skin
why change it??i love it 
It'll make it too predictable though
Wouldn't happen. Particle design has abilities look similar for similar effects for a reason. When the field is cluttered, it's hard to see what's going on at times and we need to be able to just know what's happening without actually thinking about it. Same reason the visual effect of bard's ult is the same as zhonyas.
MAKE HIM WALK LIKE A TROLL
Uh, no. What needs to happen with Zilean's ult is absolutely "duh." Stop telegraphing it to the enemy team thus rendering it practically useless.
Those particles should be various clocks. Pocket watch, Grandfather clock, Swatch wristwatch, sundial.
I can't see a reason not to do this.
Not sure if particle effects can be played in reverse in league's setup
Nice idea.
For me though, I keep asking myself if Riot will ever change Zileans overall look. To me, he barely looks like the same events character shown in his loading screen picture.
If it cant be reversed, then why dont you just play two separate animations? Code would just go like this:
Champion Dies Lets say it takes a total of 8 seconds total time for a champion to die and then come back to life 1.) Play death animation - (Lasts 4 seconds) 2.) After 4 seconds, play new animation (Which is just the death animation but in reverse) 8 seconds total.
Done.
Do 
even have death animations for this to use?
I just dance or taunt when I'm reviving
be like a travel ult
