I think I’ve got it.
I extended the select field, as per these instructions.
Created its assets folder, and added a style.css file, and font awesome css to the css folder + font awesome fonts to the fonts folder.
I then linked both css files as assets to the extended field. This is the full php field file:
<?php
class selectawField extends SelectField {
static public $assets = array(
'css' => array(
'font-awesome.min.css',
'style.css',
)
);
}
Then, in style.css, more or less followig advice from this SO answer I gave fontawesome to the ‘option’ element /edit and also to the ‘select’ element’ edit/ as such:
select, option {
font-family: 'FontAwesome';
font-style: normal;
}
Now, adding something like this to a blueprint, does actually show the icon in the dropdown select menu on the panel /edit and also on the select menu once it drops back up edit/
at least on chrome
icon:
label: icon
type: selectaw
options:
'': ''
'': ''

How about this solution?
Thank you!
/edit, just por completeness, alhough it works this solution seems to create a console warning regarding the path from the FA css to the FA fonts ; I moved the issue to a different question for clarity here, edit/