I created a scheduled job to reset the display options for all blocks within a specific page type within our site.  The job identified a list of all pages of the required type and then iteratred through the blocks in the content area to amend their display option.  Below is a copy of the job I created:

[ScheduledPlugIn(DisplayName = "ResetDisplayTypes")]
public class ResetDisplayTypes : ScheduledJobBase
{
	private bool _stopSignaled;

	public ResolveDisplayTypes()
	{
		IsStoppable = true;
	}

	public override void Stop()
	{
		_stopSignaled = true;
	}

	public override string Execute()
	{
		OnStatusChanged(String.Format("Starting execution of {0}", this.GetType()));

		List<ContentAreaItem> items = new List<ContentAreaItem>();
		var pages2Check = GetAllPages();
		var contentRepository = ServiceLocator.Current.GetInstance<IContentRepository>();
		
		foreach (var page in pages2Check)
		{
			ArticlePage writablePage = (ArticlePage)art_page.CreateWritableClone();
			ContentArea area = writablePage.MainContentArea;
			foreach (ContentAreaItem cai in area.Items)
			{
				var renderSettings = new Dictionary<string, object>
				{
					["data-epi-content-display-option"] = "Half",
					["data-contentgroup"] = "",
					["tag"] = "Half"
				};
				var replace = new ContentAreaItem
				{
					ContentLink = cai.ContentLink,
					RenderSettings = renderSettings
				};
				replace.LoadDisplayOption();
				items.Add(replace);
			}

			area.Items.Clear();
			foreach (ContentAreaItem item in items)
			{
				area.Items.Add(item);
			}

			var saveAction = SaveAction.CheckIn | SaveAction.Publish | SaveAction.ForceNewVersion;
			DataFactory.Instance.Save(writablePage, saveAction, EPiServer.Security.AccessLevel.Administer);

			items.Clear();
		}
		
		if (_stopSignaled)
		{
			return "Stop of job was called";
		}

		return "Display types updated for each block.";
	}

	private static IEnumerable<ArticlePage> GetAllPages()
	{
		var contentLoader = ServiceLocator.Current.GetInstance<IContentLoader>();
		var contentTypeRepository = ServiceLocator.Current.GetInstance<IContentTypeRepository>();
		var contentRepository = ServiceLocator.Current.GetInstance<IContentRepository>();
		var contentModelUsage = ServiceLocator.Current.GetInstance<IContentModelUsage>();
		var pageType = contentTypeRepository.Load("ArticlePage");
		var pages = contentModelUsage.ListContentOfContentType(pageType);
		var publishedPages = pages.Select(u => contentRepository.Get<IContent>(u.ContentLink))
									.Where(x => (x as IVersionable).Status.Equals(VersionStatus.Published) && !x.IsDeleted)
									.Cast<ArticlePage>();
		return publishedPages;
	}
}