Mauno,
I have been on holiday and just discovered your and Marc's questions.
First I see you have done great work to implement a flexible way of editor handling. Great.
Yes, I think the YUI-RTE should be part of the family.
No, I don't have the time got get involved into this work in the moment - sorry.
Can anybody of the experienced Moodle developers tell why HTMLarea programmed integration is done the way it is? If there are certain needs for the close integration with the existing option and you don't care for them and just replace all textareas you may break Moodle functionality.
I know that the edit page for resource "Compose a text page" now shows the HTMLeditor for the top textarea and no HTMLeditor for the bottom textarea. When you just replace all textareas with the editor you break Moodle behaviour.
Urs