OldFatGuy: B) He must not be omnipotent. Why worship a powerless God?
The Japanese, in Shinto religion, have some gods and goddesses (kami, ookami, etc) numbering 10.000.000 roughly... Numbers exactly like the population of a small country, but instead of humans, gods. They are not omnipotent, they possess various powers, specialties or fields of expertise, yet they are not so "divine" like the western equivalent of the idea of "god". Some of them can supposedly be "sealed away", drop outside favor, etc. Yet they are worshiped, receive tribute and have many festivals after them.
Also, in Goetia and the lesser keys of solomon, the "deified spirits" are 52, carry favors with proper exchange/offerings and are anything but, omnipotent... On the contrary, they are weak before not only god and beneficial spirits, but even in the presence of virtuous people (and accomplished theurgists/spiritualists).
From whence come (and with such certainty, too), that someone worships only powerful god(s)? There are countless people who worship powerless gods, even within mainstream religions and world known (and renowned) ones... Or their offshoots and hearsays (heresies/apocrypha etc).