Hi nicholas,
I believe there's a lot of hikashop user which using 3rd party Wysiwyg since default tinymce has a lot of limitation. i check on JCKEditor and JCE Editor.. and it has bugs with WYSIWYG, so using tinymce is a solution right now.
There's very simple solution on doing this, and i see you guys already prepare a neat code for this.. it took me an hour to find it, and i'm bit surprise for this simple solution and you choose not to give me a clue to find this... at least a simply reply like "you might take a look on xxxxx.php and xxxxx.php.... and can dig deep there, but we don't provide further support on this..."
Anyway.. for any of hikashop user who like to 'force' tinymce as the default WYSIWYG editor for custom field... here's the solution:
1. open administrator/components/com_hikashop/helpers/editor.php
2. find the line consist of : function setEditor($editor=''){
3. change it into: function setEditor($editor='tinymce'){
4. done
Hope this tips helpful