1. Going to assume you've never heard of spiritbonding? You can equip a set of lvl 10-ish gear and continuously oneshot low level mobs for spiritbond, then extract the materia every 5-10 min or so.
2. Light gain is already crazy fast if you just cycle through Tam-Tara/Sastasha/Aurum Vale. Possibly even Copperbell/Toto-Rak, now that both of those have been changed. Those dungeons can be completed in roughly 4-5 min, and already give a good amount of Light without bonus.
3. I'm surprised you're asking for a nerf to the costs of the books. It's 9 books at 100 poetics each. A single daily MSQ roulette will already give you 450-500 poetics (and an extra 100 if you get a first time bonus).
4. Finishing the zodiac weapon lets you buy replica versions of every single step, even the very first unfinished weapon model. They're sold by Drake, the NPC standing next to Gerolt

The only thing mildly annoying about the Zodiac weapon grind is the book part, but not really annoying enough to nerf it even further than it already has.
This is an optional grind for a glamour weapon, so I don't think it hurts for it to be slightly grindy.