The plugin doesn’t have a filter for the temp folder / temp file paths?
The PHP open_basedir config is set by a jinja template (Trellis ansible):
You would have to override it so you can specify your own open_basedir values,
e.g.:
php_admin_value[open_basedir] = {{ php_open_basedir }}
And then set the php_open_basedir variable as with other variables, e.g. to
{{ www_root }}/:/tmp:/extra-path-the-plugin-is-hardcoded-to-use/
(The path delimiter/separator in POSIX/Linux/(here) is :).