I've implemented the following regex replaces:

(?<!abbr>)([Ss])(h<hi rend="[^"]+super+[^"]+">d\.?</hi>\.?)
<choice><abbr>$1$2</abbr><expan>$1hould</expan></choice>

(?<!abbr>)([Ww])(<hi rend="[^"]+super+[^"]+">d\.?</hi>\.?)
<choice><abbr>$1$2</abbr><expan>$1ould</expan></choice>

For the record, the first one of these would find the following:

w<hi rend="vertical-align: super; font-size: 80%;">d</hi>

and mark it up like this:

<choice><abbr>w<hi rend="vertical-align: super; font-size: 80%;">d</hi>.</abbr><expan>would</expan></choice>

Changes are being uploaded to the database now. Committed a fresh revision to SVN after each operation.