Denholm, flak that's truly lethal and that follows real ballistics would be easily avoided by fighters furballing or just passing through, and really put a dent in planes flying steady towards it. We could get some extra destroyers or whatever would allow for more 5" flak.
It would make for more fighting which can only be an improvement.. There's no such thing as too much firepower.
The lengthened time it'd take to damage a CV enough to sink it would allow fighters to form a cap, which we don't have now. It would give bomber pilots a real challenge (just a thought, flak targetting could be made to spread over a tight group flying formation when there is one so that it doesn't just trounce formations one by one), bomber killers more targets, CV furballers a better chance at having their furball, and the recon thing would get another element.
Everybody's happy.