Hi, late night and on vacation but you can use something called "tags" in episerver. When rendiering a contentarea you can say that only content with a specific "tag" can be used in the area. You set this with code. If you have a look in the templatepackage from EPiServer you can find examples where this is done.

You use templatedescriptor for this and RenderSettings. Have a look at Johan Björnfots blogpost: http://world.episerver.com/Blogs/Johan-Bjornfot/Dates1/2012/9/EPiServer-7--Rendering-of-content/

He will explain most of the stuff. :)

Try the below class for controlling the Block items.

 //Original URL: http://www.menzies-smith.co.uk/?p=76
    [AttributeUsage(AttributeTargets.Property)]
    public class AvailableContentTypesAttribute : ValidationAttribute
    {
        public Type[] Include { get; set; }
        public Type[] Exclude { get; set; }

        public override bool IsValid(object value)
        {
            if (value == null) return true; // If the Content area property not have the Block type value then return true
            if (!(value is ContentArea))
            {
                throw new ValidationException("AvailableContentTypesAttribute is intended only for use with ContentArea properties");
            }

            var contentArea = value as ContentArea;

            var notAllowedcontentNames = new List<string>();

            if (contentArea != null)
            {
                if (Include != null)
                {
                    var notAllowedContent = contentArea.Contents.Where(x => !ContainsType(Include, x.GetType()));
                    if (notAllowedContent.Any())
                    {
                        notAllowedcontentNames.AddRange(notAllowedContent.Select(x => string.Format("{0} ({1})", x.Name, x.ContentLink.ID)));
                    }
                }
                if (Exclude != null)
                {
                    var notAllowedContent = contentArea.Contents.Where(x => ContainsType(Exclude, x.GetType()));
                    if (notAllowedContent.Any())
                    {
                        notAllowedcontentNames.AddRange(notAllowedContent.Select(x => string.Format("{0} ({1})", x.Name, x.ContentLink.ID)));
                    }
                }
            }


            if (notAllowedcontentNames.Any())
            {
                ErrorMessage = "contains invalid content items:";
                foreach (var notAllowedcontentName in notAllowedcontentNames)
                {
                    ErrorMessage += " " + notAllowedcontentName + ",";
                }

                ErrorMessage += " Please select ";
                foreach (Type type in Include)
                {
                    ErrorMessage += type.Name + ",";
                }
                ErrorMessage = ErrorMessage.TrimEnd(',');

                return false;
            }
            return true;
        }

        private bool ContainsType(Type[] include, Type type)
        {
            return include.Any(inc => inc.IsAssignableFrom(type));
        }

        protected override ValidationResult IsValid(object value, ValidationContext validationContext)
        {
            var result = base.IsValid(value, validationContext);
            if (result != null && !string.IsNullOrEmpty(result.ErrorMessage))
            {
                result.ErrorMessage = string.Format("{0} {1}", validationContext.DisplayName, ErrorMessage);
            }
            return result;
        }
    }

PageType:

  [AvailableContentTypes(Include = new[] { typeof(BlockType1), typeof(BlockType2) })]
        [ContentAmount(Maximum = 1)]
        [Display(
          Name = "Sample",
          GroupName = SystemTabNames.Content,
          Order = 100)]
        public virtual ContentArea Sample { get; set; }