Gatling’s core is written in Scala. It’s way easier to call Java from Scala than the other way around.
So I’d say it’s still at least complicated.
Note that I don’t know Scala and have very limited knowledge of Gatling
No offense, but I’m not sure you should try to build your own extension then.
We don’t document how to build extensions because at this point we don’t want to provide a public stable API for this. On the contrary, we want to be able to break our internals as much as we want to be able to move forward (and we do).
Either you manage to get how things work on your own by reading the code and how some people have managed to write custom extensions (the ones we’re aware of are listed in our documentation), or you can consider contracting with us so we write it and maintain it for you.