You can't do something like this using the stock HtmlHelper extension methods, but you can use the same link-generation framework the HtmlHelper ActionLink extension method is using. Under the covers, ActionLink uses a static method named GenerateLink, which does allow you to supply a protocol name:
public static string GenerateLink(RequestContext requestContext, RouteCollection routeCollection, string linkText, string routeName, string actionName, string controllerName, string protocol, string hostName, string fragment, RouteValueDictionary routeValues, IDictionary<string, object> htmlAttributes)
So, using this method (which emits a string) coupled with the HtmlHelper class' ability to emit raw HTML using the Raw method, you can write your overridden links:
@Html.Raw(HtmlHelper.GenerateLink(
ViewContext.RequestContext,
Html.RouteCollection,
"My Link Text Here", null,
"ActionNameHere",
"ControllerNameHere",
"http",
null,
null,
null,
null))