I played in a Pathfinder campaign that was very, very similar to this years ago. FWIW, here's the basic framing and my reaction as a player.
Our characters started at 1st level, we did not know that we were the remnants of gods that were sundered millennia ago. We adventured "normally" and started finding magic items that were suited to specific characters - anyone could have taken them, but the war hammer made more sense for my barbarian than for the alchemist or mage.
As we leveled up, our items started gaining abilities. At first, they were dictated by the GM. We also picked up other items, and the items started to have synergies with each other. As plot unfolded, we discovered we were the remnants, and our powers had been hidden in these artifacts when we were sundered. The party mage had, as a god back when, sundered all of us in order to keep one god from stealing all of our powers. The current campaign was our opportunity to return to god-hood, and to stop that other god once and for all. (That god was also a much weakened god when we started, but as we were recovering our powers, so was he.)
As a player, I thought our GM did an amazing job of rolling out the plot. The information we got came at times when we were getting new powers and wondered why. He also did a great job letting us make the characters we wanted and shaping his world and plot to accommodate those characters in his story. He encouraged us to think about our mythology as we developed, and we did start developing followers when we helped out someone.
The biggest challenge as a player was the item powers. Each time we leveled up, we got new powers for one or more of our artifacts. We played to 20th level, and at that point my 4 artifacts had probably 25-30 powers total, some of them interactions between items. Each round of combat I had to figure out which powers I might use, or not, and it really slowed down as we gained levels.
If I were going to try this sort of thing in RM, I would avoid adding unique abilities as they level up. Go with fewer abilities, but increase their potency as level goes up. But these are artifacts, if they're god-items. Don't feel totally constrained by RM logic/rules, though stick close to them while the characters are lower level.