Player built meta modules are on the roadmap. The “named components” are already on the market for capital meta modules.
The prerequisite is completion of module tiercide so all meta modules fit the new model described as “compact”, “enduring”, etc… CCP has been working on this for at least 3 years - it doesn’t seem to be very high priority! Turrets were supposed to be done last summer but it didn’t happen and the project hasn’t been mentioned since.
Once complete, you will purchase a BPO and build the module using a T1 module plus some named components that drop as loot instead of complete modules.
Having NPC’s buy stuff from players would disrupt the player driven market. CCP has chosen a hands off approach to the market - let supply and demand set prices - which is why it works as well as it does.
There needs to be some reward for killing NPCs and bounties are problematic since growth in the money supply is disconnected from growth in the economy. We need more material rewards that are exchanged for ISK rather than ISK itself - Abyssal rewards are non-monetary which I consider a step in the right direction. Let materials and components drop as loot while players make finished goods.