[eluser]jppi_Stu[/eluser]
Looking ahead at 2.0, I would ask whether the functions are related in a way that a Library would make sense. If so, do that. If not, a Helper would be the way to go. The ambiguous "Plugin" structure itself won't be supported from 2.0 onward, so at this point no new plugins (as such) should be created.
Libraries and Helpers are where it's at in the new world!