A quick scan of the churches, and I saw none, though there may be. So, perhaps, when you say, “unite as Christians within orthodoxy for the bigger cause of Christ”, you need to define “unite” and “orthodoxy”. There are many ways in which we are all united - baptism is a specific example. We can also be united in helping the least of His children, and defending the unborn, amongst other things. But if you mean unite at the altar, when there is no complete unity, this is problematic for (confessional) Lutherans, both scripturally and doctrinally.Are you familar with the Alliance of Confessing Evangelicals in which there are Lutherans who belong to it too?
alliancenet.org/CC_Content_Page/0,PTID307086_CHID798774_CIID,00.html
Jon