If you really want, it is not difficult to make a letterspaced font. The
Sauter cm font distribution contains the font cmrs (Roman Sperrsatz) as an
example done with METAFONT, allthough it will be more sensible and disk
space saving to do it via virtual fonts.
I don't see any need to change LaTeX or TeX (the program) in order to do
Sperrsatz (= letterspacing for emphasis). Within the NFSS `letterspaced'
can be naturally defined as a fontshape attribute, since it does not make
sense with any other shape than the roman one (IMO).