If I was a kid I'd probably call him Liver.
I guess he could be Oly, with a long o sound but it would be hard to get people to understand the difference. He could go by his initials, but not OJ or OK, and OE or OA wouldn't work too good. But really, Ollie is the only likely one till he earns himself a nn like Specs or Oliver Who Lost His Shoes On the School Trip to the Dairy Farm.
Before you criticize a man, walk a mile in his shoes. That way, when you criticize him, you're a mile away and you have his shoes!
Steve Martin