There is always the option that the presbytery could allow the man to be stated supply at a congregation while he works towards passing the ordination exams.
This is true of the PCA as well. To expand on this answer for the PCA (I think this would apply to the OPC as well, but I'm less certain, since I'm in the PCA): there are a few variations of the supply relationship, which is generally meant to be temporary, and isn't ordinarily meant to include the
full slate of pastoral responsibilities, except for a very short period of time. And all supply relationships are subject to presbytery approval, and the BCO places a time limit on it (1 year, if I remember correctly, but I haven't reviewed that section recently), but presbytery can always opt to renew it when it expires.
There's student supply, in which a ministerial candidate who has not yet completed his studies is appointed as the regular preacher for a church without a minister, sometimes with a view toward his becoming the pastor of that church upon his completion of the ordination prerequisites and exams, sometimes just to fill the pulpit at a church that for one reason or another is currently unable to secure a full-time pastor. I imagine it would be possible for someone who is pursuing ordination in another NAPARC denomination to become a student supply preacher.
There's also ruling elder supply, in which one of the ruling elders of a church without a pastor (or, perhaps even less commonly, though I know of one such case, another ruling elder from the presbytery) will serve as the regular preacher.
In both such cases, the supply preacher does not need to be ordained as a teaching elder, or even pursuing such ordination (in the case of ruling elder supply, he probably won't be). But he does need to be
licensed, because our BCO requires that any preacher not ordained as a teaching elder must be licensed, if he is going to preach regularly. And in these cases, the supply preacher may not administer the sacraments.
There is also the possibility of a man already ordained as a teaching elder becoming stated supply for one of our churches. A man already ordained in the PCA might go this route, if his relationship with the church is expected to be very temporary, or if he's not really doing anything other than preaching (though I know of cases in which a supply preacher essentially functioned as a church's pastor for an extended time; such an arrangement should be viewed as irregular, though, and a proper call should really be extended by the congregation in such a case, even if the man is only serving as an interim pastor for more than a few months).
I
believe it would be possible for a man ordained in another denomination to serve as the supply preacher in a PCA church. It would probably be a relatively simple matter to have such a relationship approved by most presbyteries if his ordination was in another NAPARC denomination. It would still be possible for a pastor in a non-NAPARC denomination, depending on which one we're talking about, but it would (or at least
should) come under greater scrutiny. I can certainly imagine a more conservative/ confessionally-minded minister from the CRC or EPC, for example, being approved. Whether or not the minister in question would be expected to transfer his credentials to the PCA would probably depend on the circumstances, but it would almost certainly make his approval more likely if it was made known that that was his intent.
All that being said, such a situation doesn't
usually come up in the PCA, just because of the relative size of our denomination--it's more common that we're the ones supplying preachers for churches in other denominations. I know of several such arrangements, but none that flow the other direction, though I'm sure there are some.
