I’m not entirely sure I follow, but I think I understand.
My initial idea was a tiddler “0” where you would use it as a directory tiddler, and all newer tiddlers would be “1” “2” etc. and you wouldn’t need to worry about titling them, and instead put your focus on quickly getting down your thoughts, and using fields for context, such as a field:tiddler-topic, field:topic-type, and field:topic-status, with each enlist’ed to allow you to give multiple of each if needed.
Your Domain, Project, Type
structure reminded me of this, however I think it follows a different train of thought that I haven’t fully grasped yet, but going on from your post, a tiddler starting at 1 wouldn’t be a problem, so long as TW recognizes the number in the title and doesn’t decide to name the next tiddler “tiddlername 1 1” as I have encountered.
It was mentioned above that you can achieve this using the unusedtitle macro, but I wasn’t able to figure out how following my tinkering with the try it buttons on TiddlyWiki.com
Unfortunately I have to head to sleep for work, but will return to this in the morning after my meetings, I look forward to picking this back up.