Another Suggestion for the American Mathematical Society

In addition to ensuring that the {subequations} environment works the way many authors think it works, it can be made more customizable by replacing the definition of {subequations} with the following:

\def\subeqform{\alph}
\def\subeqpunc{}
\newenvironment{subequations}{%
  \refstepcounter{equation}%
  \protected@edef\theparentequation{\theequation}%
  \setcounter{parentequation}{\value{equation}}%
  \setcounter{equation}{0}%
  \def\theequation{\theparentequation\subeqpunc\subeqform{equation}}%
  \ignorespaces
}{%
  \ifnum\c@equation=0%
   \setcounter{equation}{\value{parentequation}}%
   \addtocounter{equation}{-1}%
  \else
   \setcounter{equation}{\value{parentequation}}%
  \fi
  \ignorespacesafterend
}

If authors want the {subequations} to be numbered (1-i), (1-ii), etc., they can simply add:

\def\subeqform{\roman}
\def\subeqpunc{-}