Cunninghams will have that effect on sails without battens, but would do no good on a battened sail. Cats call the Cunningham a Downhaul. And the Downhaul will bend the mast and flatten the sail -- probably not what you want in light air.
The sloop mainsails are just designed that way. On my Taipan 4.9, which can be sailed as a sloop or uni, I have two different sails. One for Uni and one for sloop. Both are very different cuts and will not exchange with each other successfully.
Rick