the Esper component has been design to work with the core CEP engine. However, according to EsperTech, it should be possible to
“(…) enable any existing Esper application at no code change and ensures you can process more than what your memory can hold, yet faster than what your storage can do (…)” .
Es a consequence, I can not see, why it should not work in a Esper HA scenario. If you encounter any shortcomings of the current solution, feel free to file tickets. However, we need to make sure, that patches targeting any add-on development do not conflict with licensing requirements. If you can provide a little more detail about your intended solution, I might be able to tell you if the current component supports your requirements or if you might want to branch the code and develop proprietary add-ons due to licensing issues.