(task opened as a follow-up to a conversation with @GWicke at Wikimania)
To avoid future maintenance problems and to scale up the extraction to other languages / Wiktionaries it would be helpful to have the Wiktionary templates already include semantic information in the output. On Wikisource this has already been done successfully (in the context of ebook metadata export).
It would also be a good starting point for future Wikidata <–> Wiktionary integration work. There is already some minimal semantic information included in a few places, for example gender markers (cf. the Spanish entry casa):
<span class="gender"> <abbr title="feminine gender">f</abbr> </span>
A first step would be to formalize these conventions and implement them consistently on the English Wiktionary, then adapt the parsing code on the API side.