Is it possible to default that 'Require SSL' checked to true for newly created pages?
Yes, this is possible but not through any configuration setting unless it was recently added. I have some documentation on how to do this. The negative is you have to replace this every time you update Sitefinity. This code is from Sitefinity 8 but I don't see why it would not work for 10. These instructions are below.
Automatically setting pages to SSL requires a custom page service. This custom service overrides the default page service and sets the RequireSSL attribute to true. To implement this functionality the following code must be inserted into the SitefinityWebApp solution
public class SSLPageService : PagesService, IPagesService
public new WcfPageContext SavePage(WcfPageContext pageContext, string pageId, string providerName, bool duplicate)
pageContext.Item.RequireSsl = true;
return base.SavePage(pageContext, pageId, providerName, duplicate);