Hi
Since I asked the question I got it working. (The leaflet side definitely 100%)
I'm working on an intermittent dojo require(["dojo/ready"] issue that fail to load my own custom dojo package that use the ESRI JS API.
The times that my dojo package loads, both map frameworks work with two maps on the same page. Dont ask me to explain why one would do that... 🙂
The order of references are important it seems.
I will give a complete example once it got my loading issue resolved, just to make sure its not related.
Just an update