Hm... doesn't quite work:
I'm sorry but the picture I have in my head while reading this is just rediculous.
That's basically what Netrux already specialized in.
No more warriors, even retired ones. (I know he looks like one, but no)
I'm pretty sure that's not possible.
But I think there are a few things here that I can work with. So if I may make a suggestion for a short backstory:
Makuta Deridius was a collector with a particular interest in weapons of all kinds. It was said he kept hundreds of different weapons in his quarters on Destral, amongst them several unique prototypes that were never produced in large quantities. While he never got interested in building his own weapons, claiming it would take away the fun in hunting for new additions to his collection, he did develop great skill in repairing and mending weapons. It was this talent that eventually got him assigned to Destral's armory where he was tasked to repair the other Makuta's weapons if needed. A challenging task that nonetheless still offered plenty of free time to scour the universe for new collectibles.
When Teridax declared his plan at the Convocation, Deridius immediately saw that this new course of the Brotherhood would sooner or later involve lots of violence - and thus was the ideal way to promote the production and invention of new weapons throughout the universe. Without a second thought Deridius joined Teridax - he had never cared much for the Matoran Universe anyway.
Millennia later it was an accident that caused Deridius' death. He had been tasked to repair a new type of weapon for another Makuta, one he had never seen before. Intrigued by the design he didn't simply repair the obvious damage, but dismantled the weapon partially to learn how it worked. When he found its power source, however, and carefully removed it with his tools, this caused an unexpected explosion - by itself nothing that would have killed a Makuta. Unfortunately, there were several barrels of various inflammable and explosive substances nearby... The following detonation was so powerful it took down a whole complex of the Destral fortress and it took weeks until the blackened remains of Deridius were finally found.
What do you think?
Oh, and he doesn't have to have an assigned region - simply write "None" in that case.