Round One KS
Round Two no KS
Setting Los Noches
If it's post-Hogyoku, he could nail this easily in both scenarios considering he can casually bust cities with Fragors in his Monster form.
Pre-Hogyoku, I'd have to think about it more without KS since I don't recall Aizen having many reliable options for ranged combat. But he could easily take the match with KS since Piccolo would lack a means of getting around the shikai's effects very easily.
Didn't Aizen lose the ability to use his zankpatou's powers after being rejected by the Hougyoku?
And my assumption with post-Hougyoku was when Aizen fused it with his body and up to his battle with Dangai Ichigo. Otherwise from what I'm digging up, he hasn't been mentioned much since his sentence.
@GeneralVan: Judging from taichokage's explanation, Juha seemed unsure of what exactly he experienced when he met with Aizen, leaving the details of what happened vague and no way to tell if whatever Aizen did (if he did something) would be of practical use for a battle scenario.