To do what you want to do in FTM, you would need to enter the name in the Description field of the fact / event you are describng:
Fact: 1850 Census
Place: Eaglesville, Smith, Kansas, USA
Description: 23 yrs old, single, "John Smythe", farmer, no RE or PP.
Proposing to have a Name field (in addition to date, place, description) as part of a Fact is actually not a bad idea. I kind of like it. But FTM doesn't provide that, so you would have to put it in the description field - not the source text section.
To enter as a source in FTM won't work because FTM uses Endnotes for sources. Folks would have to continually refer Page from pg 24 to pg 772 of your 1,000 page report to see your obscure notation of the name - and then other sources for your various names for that person would be in other sources who knows where in the long list of EndNotes.