Hi there,
I am Ahmed an embedded systems developer, with a Master degree on EE.
I have read your project requirements and I understand that you want to integrate a third party MQTT broker to pub/sub to the original AWS broker.
I have a solid background in programming with python and C/C++, and I have worked on several prototyping project that are based on Arduino, esp boards and rapsberry pi.
contact me over chat with more details on your project.
I hope to hear from you soon.