public class MainRouteBuilder extends RouteBuilder
{
    public static CamelContext camelContext;

    public static boolean returnLabel = true;

    public static RouteBuilder nestedRouteBuilder;

    @Override
    public void configure() throws Exception
    {
        System.out.println("Building main route!");
        System.out.println("Context: " + getContext());

        camelContext = getContext();

        from("direct:cloudAdministrationRoute.createTenant")
        //3. I do not actually want to instantiate RouteContainer like this each time I call this route.
        //I would simply want to reuse a reference to an instance I created outside of configure()...
        .to(new RouteContainer().getMyRoute(2))
        ;

        returnLabel = false;

        //configure direct:myRoute.2

        includeRoutes(nestedRouteBuilder);
    }

}

public class RouteContainer extends RouteBuilder
{
    public Route route;

    RouteContainer() {
        super(MainRouteBuilder.camelContext);
    }

    String getMyRoute(final int n) {

        if (MainRouteBuilder.returnLabel && route == null) {
            route = new Route() {

                @Override
                public void configure()
                {

                    System.out.println("Building nested route!");
                    System.out.println("Context" + getContext());

                    from("direct:myRoute." + n)
                    .transform()
                    .simple("number: " + n)
                    .to("stream:out")
                    .process(new Processor() {
                        @Override
                        public void process(Exchange exchange) throws Exception {
                            Response response = new Response();
                            response.setStatus(Status.SUCCESS);

                            exchange.getOut().setBody(response);
                        }
                    });
                }
            };
        }

//1. works:
        MainRouteBuilder.nestedRouteBuilder = this;

//2. does not work:
//      RouteContainer routeContainer = new RouteContainer();
//      routeContainer.route = this.route;
//      MainRouteBuilder.nestedRouteBuilder = routeContainer;

        return "direct:myRoute." + n;
    }


    @Override
    public void configure() throws Exception {
        if (route != null) {
            route.configure();
        }
    }

    public abstract static class Route {
        abstract public void configure();
    }

}

Building main route!
Context: SpringCamelContext(camel-1) with spring id org.springframework.web.context.WebApplicationContext:/sample-route
Building nested route!
ContextSpringCamelContext(camel-1) with spring id org.springframework.web.context.WebApplicationContext:/sample-route

{"status":"SUCCESS"}

org.apache.camel.component.direct.DirectConsumerNotAvailableException: No consumers available on endpoint: Endpoint[direct://myRoute.2].

public class MainRouteBuilder extends RouteBuilder
{
    public static CamelContext camelContext;

    public static boolean returnLabel = true;

    public static RouteBuilder nestedRouteBuilder;

    RouteContainer routeContainer = new RouteContainer();

    @Override
    public void configure() throws Exception
    {
        System.out.println("Building main route!");
        System.out.println("Context: " + getContext());

        camelContext = getContext();

        from("direct:cloudAdministrationRoute.createTenant")
        .to(routeContainer.getMyRoute(2))
        //I may want to call it again like this:
        //.to(routeContainer.getMyRoute(3))
        ;

        returnLabel = false;

        //configure direct:myRoute.2

        includeRoutes(nestedRouteBuilder);
    }

}