yes i agree.. i have used htmlArea before , i had one webpage with 52 (!) textareas and the first time i tried htmlArea i waited 25minutes before all those 'editors' got loaded !!
what i did was put a text link next to each textarea field : 'load WYSIWYG editor' : and then htmlArea would only load into that one textarea field.
i'm new to moodle but if there is only one textarea on a webpage it's not too difficult to write the link itself , it's just a link ... the 'headache' would be in tracing through the php code that generates the webpage headers and put a 'switch' function that would make that link work!! every webpage has a header and browser versions force moodle to 'jump through hoops' already to deliver webpages with the right header for different browsers ... ;-} ... moodle is a 'big' website even before your courses are created and your educational content is added...
the wysiwyg editor is terrific, i love it and am incorporating it as my 'Slide editor' in the chat module enhancement i am coding right now....
but i think having that 'load WYSIWYG editor' link is a great idea , then you would not 'remove functions' when you set your moodle config to not use the editor, it would be a question of 'load by default' or 'load on demand'.