There is the idea of one deity being split into several others
That's something frequent in Hinduism and in Egyptian mythology, but I'm not sure how well it works for others.
Alternatively, you could have multiple deities take up the same roles and similar names in succession to one another, i.e. the name "Odin" being passed down over many generations.
Heeeh, not sure about that one. Generally, the appeal of multiple pantheons is seeing the gods you know interacting with each others. It's less interesting if the Odin you meet is not
really the original Odin, but, say, his son Vidarr taking up his role after Ragnarök.
Yeah, like, what? You think Zeus would truly allow people to forget him? There'll be annual celebrations, where he goes across the world in a trail of hurricanes and blazing divine power, reminding all of his power. The celebration will be public, very public, and everyone in greece or rome would know of it. He would go to every town and.....
A bit unrelated to the main subject, but since you mentionned Zeus, in the case of Classical/Graeco-Roman religion, a widespread school of thought was that human wickedness had resulted in the disappearance of the gods, leaving mankind behind to let it destroy itself. It first starts, and is arguably based, in Hesiod's poem
Works and Days, where a prediction is made of the divine departure as Hesiod explains the five Ages of Man: the Golden; the Silver; the Bronze; the Age of Heroes (which was brought to an end by the Trojan War/return of the Heraclids); and the Iron Age, in which Hesiod lived and which continued in increasingly worsening conditions.
Works and Days forecasted that, later on in the Iron Age, the goddesses Aidos and Nemesis, of shame/modesty and vengeance respectively, were going to shroud "their sweet forms in pale mantles" and escape from the world and its corruption to go up Mt. Olympus, forsaking "humankind to join the company of the deathless gods, and leaving nothing but bitter sorrows for mortal men. And there will be no help against evil."
In the
Description of Greece 8.2.4-7, Greek geographer Pausanias offers his opinion on the issue by commenting first on the story of Lycaon,
one of the first werewolf supposed to have been turned into a wolf by his own grandfather Zeus, after the god had visited his house for a meal and he gave him his own son. He alludes that the gods no longer act directly in the physical world, but give punishment in the afterlife:
Description of Greece said:
For the men of those days, because of their righteousness and piety, were guests of the gods, eating at the same board; the good were openly honored by the gods, and sinners were openly visited with their wrath. As a matter of fact, in those days men were changed to gods, who down to the present day have honours paid to them—Aristaios [Aristaeus], Britomartis of Crete, Herakles [Heracles] the son of Alkmene, Amphiaraos the son of Oikles, and besides these Polydeukes [Polydeuces] and Kastor [Castor].
So one might believe that Lykaon was turned into a beast, and Niobe, the daughter of Tantalos, into a stone. But at the present time, when sin has grown to such a height and has been spreading over every land and every city, no longer do men turn into gods, except in the flattering words addressed to despots, and the wrath of the gods is reserved until the sinners have departed to the next world.
The Roman poet Ovid takes this up in his poem the
Metamorphoses, wherein he says that it was during the Iron Age, perhaps at its onset, that Pudor, Veritas and Fides (Modesty, Truth and Loyalty, whom the Greeks would have called Aidos, Aletheia and Pistis respectively) were the first virtues or powers to flee from the world. The situation got gradually but dramatically worse before finally Pietas (Piety) was vanquished and Astraea (a Titan goddess also referred to as Dike, or "Justice") became "last of all the immortals to depart" and "herself abandoned the blood-drenched earth."