This was a concern to me as well, I thought about the possibility of a different "currency", but based on leaks it looks like bojo and gojo are already a system alongside mojo (pojo).
Having a fourth currency seems kinda overkill.
The main things that inspired me to draft it up, outside of "I just think it's cool" was the fact that some books feel bad to use, and most people just stick to the same few books. After using speed for so long, digging with mainhand nav feels exceptionally bad, even with the base's mojo speed boost, so I was looking at ways to gain small passive benefits that would persist despite books chosen.
I also thought it would be cool, allowing players to "branch out" past books, allowing them to tailor their playstyle to their own priorities in a way that isn't present with books. Typically people run the same 4 things: Gambler/Midas - Celestial - Nav/Speed - Pio
It would also incentivize grinding more, as it would be a overall goal to work towards past just "get 2 mojo for endslate" or "get x mojo for pickaxe". It would allow for smaller incremental steps, where each mojo would feel like you've earned something. Currently the first mojo feels like a bait to use, and it really takes 2 minimum to get started.
The last reason was the social/math aspect of it. I'm a huge nerd who will spend hours theorycrafting in games. Sometimes it's more fun to me than actually playing. It would allow a thriving social aspect where people could discuss their builds, working together to optimize or discuss the benefits of "luck" over "mining speed"
The hope was by "locking it behind a mojo" it would be a system only accessed by players that have a bit of experience, so they'd not easily be overwhelmed.
This isn't meant to be a push to move this forward. Just wanted to share my thoughts on the creation process for all to see!