Actually, it will technically be legal to unloaded open carry in a locked case, so if you had a case where you could see the gun in it while it was totally enclosed, (in a transparent case, for instance) it should be legal.
Also note, that while in the past, it was explicitly said that a firearm carried openly in a belt holster was by not considered concealed, this wording is repealed next year. (I'm not sure if that wording had much effect anyway... it did not require one to carry openly in a belt holster, it merely bolstered that mode of carry.)
However, concealed and unloaded in a locked case and you must rely on additional exemptions, such as traveling directly to or from a vehicle. Personally, I would not be willing to risk locked unloaded concealed carry. Especially if you do it as a form of a protest and tell people there is a gun in the case, you will give up your 4th right against search and seizure, which is the main thing preventing a prosecution, it seems to me, unless if you can prove that you are indeed not just standing around protesting in a public square but actually moving from your vehicle directly to some other place where you have any lawful purpose to transport the gun to.
You can however, carry openly or concealed without a locked case any firearm with a barrel over 16 inches long, so long as the firearm is not designed to be interchanged with a barrel of a shorter length. There are some super long barreled handguns out there.