>  I suggested LaTeX should have a PlainTeX class, so that could
> conveniently migrate from PlainTeX to LaTeX...

I find

latex &plain  file.tex

usually works quite well.

You can also go

which works most of the time as well. But probably not for the kind of
article that appears in TUGBOAT. It is not too hard to write a TeX
document that really excercises the obscure bits of whatever format it
is aimed at, and so really will not run on any `emulation'.