But he wouldn't! Be an ensign.. he would no longer be in Starfleet and be one of those outlier crew members like 7 and Neelix. Because he was old Harry who had gone through real shit rather than just problems with his mother it would be a total reboot of his personality. Harry 2.0. This would have been pretty awesome.
(Seven and Chakotay enter the meeting late) Janeway: Where have you two been? Old Kim: They're having sex.... (mutter... jealous... mutter....)