I'm going to pimp 1.10 Sprout (I'm partial to Scavenger Mode).
It has a very Vanilla feel to it, in that progression isn't just a mad rush up one tech tree after another. It also isn't a grindfest, while finding other ways to slow progress. So far as mainstream tech mods, you'll likely find it underwhelming (AA, Immersive Engineering, RFTools, EnderIO), but that's actually one of the reasons I fell so deeply in love with it. The tech is there, but it is sometimes gated behind walls other than just more tech. It has been the best showcase of magic mods in 1.10 that I've seen, and has actually convinced me that magic in Minecraft didn't die with Thaumcraft.
You want to build a castle. No problem, building castles can be done in nearly any pack. You want your castle to be surrounded by a village. How does MineColonies ability to make functional town's that grow as you do sound? Automate mining with a villager who actually digs a mineshaft and branches out on his own, stopping when he needs food or a new pickaxe. Supply him food and pickaxes with a delivery man and warehouse. Feed the warehouse bread from your Baker, who gets wheat from your farmer. A living breathing town, where you get to choose building placement and some degree of floorplan, all built by the villagers themselves (ok, the builder does all the construction work, but he's a villager too).
Your friend likes to hunt and kill. There is a Slayer's Guild who will pay him coin to rid the world of the monster threat, including hunting dragons (which you can find an egg and raise and eventually ride). An RPG leveling system allows each player to focus on different traits, with classes that get perks for different activities (warriors get extra XP from mob kills, miners get a chance for double ore drops when mining, etc.). There are a number of boss fights in the world as well, spread through Recurrent Complex structures across the world.
A quest system exists, but it's all immersive by CustomNPCs dialogue. The needs of different NPCs will force you to explore to find solutions or even other NPCs who may have more work for you.
Silent's Gems offers versatility in weapons and even armor, with abilities that increase as your infrastructure and resources improve. An equipment leveling system makes using even outdated equipment sometimes worthwhile, which helps balance the overall armor/weapon progression as well.
Did I mention magic? Botania, Blood Magic, Ars Magica, Astral Sorcery, Roots, Ice and Fire... Most, if not all, have their own in game documentation, making entry level players feel more at home getting started.
It's truly a different experience from any other pack I've played, but it is most certainly still Minecraft. I highly recommend it (if you hadn't noticed).