I always thought the Cooper's OS lager needed some hops. And since it uses an ale yeast,it's actually a light colored pale ale. 2oz of English hops would be good. You could make a 15 minute tea with the hops at the begining of the boil for 15 minutes. Then remove the hops & add your fermentables off the heat. You never boil pre-hopped extracts. Then chill & top off in the fermenter & stir or shake to combine before testing & pitching.
Ot you could look at my recipes for how I use their cans with plain DME & hops to make them better.