I would suggest not having your pages derive from Standardpage(PageType).  I would create an abstract class called BasePageType and derive your pagetypes from that.  Then you would have a standardPage(PageType) derive that that with no properties in that.

public abstract class PageTypeBase : PageData
{
[Display(Order = 1, Name = "Page Title", Description = "Used as the headline on each page"), CultureSpecific(true)]
        public virtual string PageTitle { get; set; }

        [Display(Order = 500, Name = "Main Body", Description = "The page text"), BackingType(typeof(PropertyXhtmlString)), CultureSpecific]
        public virtual XhtmlString MainBody { get; set; }
}

[ContentType(DisplayName = "Standard Page", GUID = "0b97d3d3-648f-4faf-839c-49e93a2b1b15", Order = 1)]
    public class Standard : PageTypeBase
    {
    }

Hi Thomas

If I understand your problem correctly you are probably looking to use IncludeOn which allows you to specify which parent page types you want your page to be allowed under.

See my blog post for an explanation of this and also a comparison to PTB: http://www.david-tec.com/2012/06/Comparing-PageTypeBuilder-and-EPiServer-7-Preview-typed-pages-part-2-of-3/

David

Thanks for both your comments. I had already considered both alternatives, and for now my workaround is Alternative 1, move the properties to an abstract baseclass and change the inheritance. However, I can think of a couple of reasons why that's not a good idea in the longer run.

The IncludeOn works of course, only that I would prefer to put the pagetype availability settings in one place, on the parent level. 

I guess I'm saying I would like to see the Availability.Specific to really mean SPECIFIC page types, and perhaps an Availability.InheritedFrom enum for how it works today.

I am not sure I understand.  You put the Availability on the Sepcific PageType.  You just leave the abstract class alone. What are you seeing when you put the availablity on the pagetype.