Even then, I could still see him saying no.
Maybe he did try and fail. Who knows?
So here's a question: why didn't he just have the Lion Turtle do it for him?
I think the fact that he didn't do it it pretty solid proof that he either couldn't or wouldn't because judging by the number of air acolytes, I doubt he would be left wanting for volunteers.
Maybe he could but didn't think it was his place to play god. Maybe the Lion Turtle specifically told him not to. Or his past lives for that matter. Hell, for all we know his energy bending can only sever or restore that which was there to begin with, not create something entirely new. Actually when you think about it that's pretty consistent with the normal bending disciplines.
Maybe energy bending can't create energy just as water benders can't create water, earth benders don't make the land, not can an air bender spontaneously generate air. Fire benders are a bit of an anomaly in that regard but IIRC it's not that they create fire so much as they draw on their body's internal heat and electricity then channel and focus it to make fire and lightning....Yeah, I know. :/