I am not a coder, but I can probably help anyways for development. 
I have CentOS systems at work which I can happily run tests against with large real-world data. They are development systems I can trash. 
i can't change CentOS that easily (maybe I can use virtual machines), but I can put whatever version of MariaDB on my systems and runs tests against it. 

If someone wants me to run tests, let me know. 
When the Aria tables can be used with MERGE, I will be very very happy to test it using a terabyte of data. The Aria engine has some some advantages over MyISAM and InnoDB for some report servers I wish to setup. MERGE is one of the last things for me to recommend it. 

Anyways, any testing is fine with me. I only have CentOS systems though. 

Mark