I could not see a workable path using some mix of the rails queries suggested by @pfaffman but his subcategories prompt was very useful.
I was reticent to Allow duplicate topic titles as @Moin suggested but turns out the result was not confusing, at least to me, as I feared it would be.
So… category A for the original bill, two subcategories for Law as Amended and Impact, create new mirrored tag groups for the two subcategories using existing tags, then create new topics with placeholder text for each of the Sections of the original bill. This part is rather brain numbing 
given the there are 307 sections/topics in category A. 614 manually created topics, yikes.
I thought turning off Allow duplicate topic titles would be best once we open the forum to users but I believe that would make any edits in the topics un-savable which won’t work with topics as wikis.
In practice allowing duplicate titles may not create the confusion I fear but..
Does it makes sense to have warning that prompts the user to adjust the title instead of just allowing the topic save to proceed? Maybe something similar to:
But with different text and selecting OK saves the topic.
“The topic title you are attempting to use has been used at least once before. Please consider revising the title or, the duplicate title is needed or desired, please proceed with the save.”