Hi There!
Great coffee is certainly something that most expats living in Montenegro love... The choice is still quite limited, and in my personal opinion would be great to have a real coffee shop... but you need to keep in mind that coffee here sells for 0.80€-1.20€ and locals are unlikely to spend more.
I'm currently working on a project including a co- working space + yoga studio with a coffee / juice bar / healthy food corner in the same building. Maybe we can have a chat so you can tell me more about your idea,
Cheers! Carine