If we use C++, we get a lot of power, but it'll be very complex code. People know C++, and it's what BTC was written in. Java is slow, but most people have the runtime and out of all these options, it likely has the most developers. It's also very high level. NodeJS is built for the web, but most users don't have it. We'd need a framework like Electron to get a GUI up. It's simple, but not the fastest. Nim (https://nim-lang.org) is known by very few people, but if you guys don't know any languages/only ones you rather not user, it's easy to learn, is as powerful as C++, syntactically closest to NodeJS/Python, and as high level as Java. It does lack support though as it's a relatively new language.