Open Communion is clearly out of the question just on that principle alone. It is something the church does. To establish the truth or validity of by presentation of argument or evidence. Of course, universal, invisible church adherents believe that all the saved are in the church, whether baptized or not. They would argue for Open Communion.
Church members are under the nurture and discipline of the church in which they hold membership.
Outside that setting real nurture and discipline would be difficult to achieve. 1 Corinthians 5 is a chapter which includes references to church discipline. Baptists saw here a reference to the Lord's Supper. So, it is not just a matter of someone examining himself and deciding that everything is okay. That, no doubt, was what they had already been doing.