First, thank you very much for appreciating our mod! We will do our best to keep updating. We are glad to consent you transfering TU to HOI4. However, there is a problem: HOI4`s playing style is totally different with EU4. What we implemented here might be hard to 100% transfered to HOI4. For example diplomacy, religion, government and interaction with outworld countries. I personally think it`s impossible to 100% copy everything to HOI4. I looked at your idea, it seems you only want to reference our map and create a new mod with only Gensokyo as map. For that, my comment is:
1.You can use all the ideas in our mod. Like national flags, ideas, etc. You are free to make any change you want. But we are not responsible for any content of your mod. I think it`s impossible to copy entire our mod`s content to HOI4, so you must make some big change to fit HOI`s enviroment.
2.Actually, there is already a Touhou mod in HOI4. Here I give the link of it:
https://psteamcommunity.yuanyoumao.com/sharedfiles/filedetails/?id=1100200730
Unfortunately it is not in English but Chinese. But the modder is willing to have speaker of other language to help him complete the mod. If you are interested, you can contact the creator of that mod Nc.
By the way, that mod, in my opinion, is really really fantastic and exquisite. It perfectly merged Touhou and HOI4. To make Touhou characters more fitted in the HOI4 background, the modder even wrote a new scenario for it, which is not even Comrade and me can achieve. I highly recommend you to look at it even just in a player`s perspective.