Right now you have to use java based indicators which means rewriting the MQ4 code to java to use custom indicators. Mark has said before that there will be some sort of service that helps people convert their indicators to java to assist with this. So far, this is the only way to do this because there would need to be some code work done that auto converts mq4 to java which is intensive. Native MQ4 support would be amazing but I don't think it'll come based on what Mark has said in the past.