Don't get me wrong, but i don't quite follow your reasoning here. What makes you think that you can't go and use Composite.Core.Routing.PageUrls and Composite.Data.Types.IPagePlaceholderContent? Just because they are hidden from default intellisense in Visual Studio? There are plugins to turn that off.
Ie. for reusing content, just use this code
public XHtmlDocument GetContentFromPageAndPlaceHolder(Guid pageId, string placeholderId)� { using (var data = new DataConnection()) { var placeholder = data.Get<IPagePlaceholderContent>().SingleOrDefault(c => c.PageId == pageId && c.PlaceHolderId = placeholderId); if (placeholder != null) { return XHtmlDocument.Parse(placeholder.Content); } } returnnull; }