The King has spoken, my life has been saved! 
I can fully buy into the logic you have outlined, and it makes perfect sense!
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How about:
decimaliste ?
According to this dictionary, decimalist has meaning in British English (https://www.collinsdictionary.com/us/dictionary/english/decimalist) as " a person who is in favour of decimalism". With decimalism defined as: “a method or practice based on units, divisions, or multiples of ten”
So I add an “e” as a bit of an embellishment.
Although I understand your point of view, perhaps it’s the differentiation that would set this system apart from all the others. After all, it’s designed to organise our lives, isn’t it? It can never be too personal.
As far as the index is concerned, I’m surprised that nobody, unless I’m mistaken, has mentioned Vannevar Bush’s Memex. In any case, memory seems a good semantic field to explore. As a last resort, we’re left with Johnny Mnemonic. 
Another idea I thought of. Instead of:
- "The Johnny.Decimal System”, and
- "Your Johnny.Decimal System”.
I came up with:
- “The Johnny.Decimal Way”, and
- "Your Johnny.Decimal System”.
I just kinda like the way that sounds. It is inspired from something the owner the company I work for said when we came up with some shortcut ways of doing a job. He said, yes it will work, but “it’s not the [company_name] way”.