🚀 go-pugleaf

Since the parentage of nroff is in question...
I have two unfair advantages-- I was around when it was
born, and I have access to the on-line data base of
all Bell Labs memos ever written.
runoff was the original grandaddy. I recall it was written
by Salzer at MIT in the 1960's. Generated fixed-width
line printer output, but did right justification, vertical
spacing, etc.
The date on the first nroff memo is 1973. It was intended
to take advantage of the Model 37 teletype, which had
lower-case letters (a breakthrough!), half-line spaces,
reverse line-feed.
The first troff memo is dated 1974. It was designed around
the features of the C/A/T phototypesetter (no lasers then--
it had a rotating wheel with tiny film images of the
characters.)  Joe Ossanna wrote both programs.
The essential difference between nroff and troff is troff's
ability to handle variable-width characters, and to move
freely around the page vertically and horizontally in small
increments (1/720 inch). Thus, a "fancy" nroff that takes
advantage of new printers would, in fact, be troff.

Were the original poster to do the modifications to nroff
he suggests, he'd get ragged right margins only, since
nroff believes all characters are equal width and
adjusts accordingly.
For those who still want to venture into this,
it is very easy to modify the troff font width tables
in DWB 3.1 and 3.2 (they are readable ASCII files in
a self-evident format) to agree with your favorite
printer, call it prt. Then "troff -mm -Tprt file | dnroff"
would do what you want (need width tables under
/usr/lib/font/devprt).