Mod adds additional story and purpose for a survival single player game, reason to mine much ores, reason to enchant and build grinders, the list goes on.
There are many extensions to this, but the initial two are the big ones, I'll leave out details to be brief.
A pre-made village spawns in every new world within a certain radius of the world spawn.
Player finds thia zombie-proof village and through books in chests, (or npc villager dialogue?), Learns the chiefs daughter was captured and in prison in enemy castle. Player gets directions to enemy castle from this village.
Pre-made Castle spawns in world, just like village, and has custom mobs in each level of it. No breaking blocks etc, player fights their way in, kills boss, rescues village chief's daughter. Hoorray. Party. Fireworks.
If its possible to make the village randomly spawn within a certain minimum and maximum radius of player, example atleast x blocks away but max x blocks away, then it could be challenging and fun to find, and then have a book generate in the village chest (or the npc dialogue change accordingly) to always give the coords to the castle which would be even farther away so that you rarely discover it accidentally.
The mobs in the castle don't have to be numerous, just a forced pathway for the player to follow, running into a few mobs at a time that are more strongk and make players rekt unless they have max enchanted diamond stuff and potions etc. Hence the purpose the the vanilla mining and mob grinding.
I have many more ideas to extend the purpose of lots of basic things in minecraft, so that one can feel a purpose to doing it all.
In summing it up.
1. Village and castle, pre made, always the same, spawn in the world at start.
2. Player finds village, to find castle, to save damsel.
3. Player must collect resources and build up in order to defeat mobs in castle.
This is just the basic idea, there are lots of ways to add a bit of story to make usual ssp stuff more worthwhile. As far as the dialogue etc, I can write all of that, its just the coding to get the village and castle to spawn, books to always spawn with certain info, etc that I need. Even the village and castle, I can make those or go to the community for them.