The game's tech tree setting will be from the 17th century to the current day.
well, like Skyrim and other 3rd-person, open world and RPG games. The control should be somewhat simple. You're human and only starts to learn magic after entering the Colony so any fighting would be more physical combat rather than a bunch of spells filling your screen like in WOW. It would be beautiful if the fighting could make use of real life martial arts logic and philosophy (like divide into different stances, the use of balancing-imbalancing, etc)
like Minecraft, just much more realistic and beautiful. Structures are held by physics laws unless they are enchanted with magic. Replacing simple blocks with various complex model like column, beam, tiles, brick, etc. Building would then require more consideration while still fun and cool as hell. You need to get and process raw materials to turn them into those "building blocks" and then can proceed with your own design. Building round and curvy shapes is no longer tricky. You can chose to put the material in any degree you want making diagonal lines possible as well. The only things that limit you is the techniques to process certain materials into certain "building blocks" that can be unlocked through a ARCHITECTURE tech tree.
Territory: after exploring for a suitable land, you start to establish your LAND. Your land is where your influence is 100% and wild animals and youkais will stay away from it. Your land will also generates resources for you. At first, your land will only be an small area around your base flag. To expand your area, there're several ways. One is to build structures outside your land and protect said structures from harm until your influence in that area reach 100%. Another way is to level up yourself and your influence will spread. You can also buy land or invade and annex lands from others. Your initial land surround your base cannot be invaded.
Production: pretty simple: raw resources/material + tech tree progress + your level + certain structure = product. Example: iron ore + blacksmith skill lv 1 learned + level 2 + smithy = iron ingot. The game only gives you the very basic of the required building, you can build over it to create a much more beautiful buildings later if you like. Remember that buildings required for certain product also needs certain requirement. Example: smithy needs a chimney so you can't cover up the chimney.
Trading: there are several "merchants" in the game from whom you can buy stuff. Rinnosuke for general stuff, Patchouli for magic-related stuff, Yukari for !@#$%^&* :)). Players can trade with each other too. One of the primary income source in the game is from selling stuff to the "merchants".
Diplomacy: there're 4 factions that already established themselves in the Colony. they are pretty powerful and acts as de facto governments. The SDM, the Moriya shrine, the Eientei, and the Myouren temple, . You can choose to ally with one of these factions if you want. If you ally with one of them, you can get both positive and negative bonus. Each of these factions has a powerful army as well with their basic units patrolling their cities that you can always fast travel to (thanks to Yukari gap technology). The basic units: SDM - fairy maid (these girls will looks like British Redcoat with fairy wings), Moriya shrine - yamawaro/kappa foot soldier, Eientei - naginata/yumi/matchlock tanegashima-wielding white hare, the Myouren temple - warrior monk.
Raising army: you can raise your own army consists of youkai (because the spellcard rule does not apply here, the army is made of youkai so they can generate after defeat. Don't worry no one is harmed). Gaining units is simple (through the tech-tree of course) so I won't talk much here. Once engage in a battle, you can either auto-resolve or fight it yourself. Once you choose to fight the battle yourself, the game pretty much turn into real-time strategy with consideration for morale and other stuff. After the battle, your units need time to replenish themselves so you won't lose a single one, thats the difference with RTS games. You are only given a limited slots for your army though so raise your army carefully. Once your slots are full, you can give your weaker units away for the "merchants" or for the factions (if you're in alliance) as mercenary so you can empty some slots.