I would create a property on the start page of type "Page", which means the property will have the type PageReference. Then it's no longer hardcoded.
It's also common to move such "settings" properties to a separate Settings page type which is itself linked via a property from the root or startpage (which are constants).
Im writing from memory so excuse any mistakes in the code.
var startPage = DataFactory.Instance.Get<StartPage>(PageReference.StartPage);
var settingsPage = DataFactory.Instance.Get<SettingsPage>(startPage.SettingsPage);
var blogPageRef = settingsPage.BlogPage;
Where SettingsPage and BlogPage are defined
public virtual PageReference xxxPage {get; set; }
in your page type class.