I think it's perfectly fine and you've been very clear on your intentions from the beginning , i mean you have to take the resources you have and make a great single player game and don't waste them to make a MMO because it's not your plan and also for us is like that , BUT even I (and my friends, and a large chunk of community from what i get) would like to put their hands on your code/engine/etc somewhere in the future and play and customize.
This means basically, allowing us to modify to the smallest detail (this doesn't concern modding tools really , it would be a plus but there's plenty of people capable of modify the code or add new things), that means also disabling the physics for most of the assets or disabling most of the AI wich makes things develop on themselves (if someone wants to implement a server/client model to make his own persistent world and then release it for everyone why not?).
Also means a whole lot of other things like no fixed map size , prevent modders from crashing their heads on hardcoding etc.
In the end you don't do it , but let us do it
, if you think about it modding capability is what has made bunch of great games a cult and making people know and enjoy them years after release (many years for some and that's the point
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