Well you certainly can have runes and jungle paths that make a champ like Kayle very aggressive in the early game, and use her to gank often. Her kit just doesn’t support it that well because her much needed waves won’t be available to her until lvl 6, and most junglers (and laners) can take advantage of her squishyness and short range to invade her often and kill her during ganks or during said invades.
If they made Kayle slightly tankier and gave her Q a small amount to the damage then I can easily see Kayle being picked in the jungle. The problem is that her kit is designed to be a scaler, and those types of junglers aren’t exactly the best ones right now. The current “meta” in jungle seems to still be the early aggressive gankers from what I can tell.
You do you, I’m just saying that you shouldn’t be surprised if it backfires and that kayle’s kit isn’t exactly designed to be as aggressive early. Know your champ’s strengths and weaknesses and you will certainly win lots of games. Good Luck with Jungle Kayle!
(That last comment was not sarcasm in case you are wondering, I am actually supporting you with this but I am just reminding you and other players of her easily taken advantage of weaknesses)