Create a snippet, call it lingua.getValue
This is the code:
https://github.com/goldsky/Lingua/blob/develop/core/components/lingua/elements/snippets/lingua.getvalue.snippet.php
On your wayfinder's rowTpl, change the placeholder, like this:
<li[[+wf.id]][[+wf.classes]]>
<a href="[[+wf.link]]" title="[[+wf.title]]" [[+wf.attributes]]>
<-- [[-+wf.linktext]] -->
[[lingua.getValue:default=`[[+wf.linktext]]`? &id=`[[+id]]` &field=`pagetitle`]]
<!-- rowTpl -->
</a>
[[+wf.wrapper]]
</li>
In here, I'm disabling <-- [[-+wf.linktext]] -->
Cache it away, the resource will be stored in a different cache key anyway.
Btw, Lingua only stores these fields:
'pagetitle', 'longtitle', 'description', 'alias', 'link_attributes', 'introtext', 'content', 'menutitle', 'uri', 'uri_override', and 'properties'