There are three issues that come to mind as potentially halachically problematic"
- Marith A'yin (creating an impression of wrongdoing) by making it seem that you have been ordained by a Christian church (see e.g.
DanF's objections in the comments to the question) and endorse
- Marith A'yin that you are engaging in dishonest practices by making use of loopholes in laws designed for religious clergy in
order to, e.g., take advantage of tax benefits. (This is probably
the weakest argument since if the law allows it, what makes it a
- Actual association with a heretical cult inasmuch as modern conceptions of ethical pluralism are in sharp contrast with the ethical pluralism espoused by the Torah. Kol hamodeh ba'avoda zara kofer b'chol hatorah kula - to acknowledge idolatry is to deny the entire Torah. (In addition, I believe issues have been raised by contemporary poskim regarding joining interdenominational organizations, presumably for similar reasoning.)
A better idea might be to develop an Orthodox Jewish equivalent ordination, perhaps offered automatically at Bar/Bat Mitzva (when the typical Orthodox Jewish boy/girl already know more about halacha than most Reform rabbis). Considering that the Jews are meant in their entirety to be a mamlecheth kohanim w'goy qadosh ("a kingdom of priests and consecrated nation"), this actually seems entirely appropriate.