what-you-see-is-what-you-get edit program?

Can anyone tell me if there is already in existence an editor program that 
enables one to edit mediawiki pages in a "what you see is what you get" mode 
(editing for dummies)?

I have an associate who says he could build such a program quite easily. 
I'm thinking, if it's so easy why hasn't it been done; surely it has been 
done; if so, where?

Thanks

Sterling D. Allan
Executive Director, PES Network Inc
http://pureenergysystems.com
http://freeenergynews.com
http://peswiki.com
http://pesn.com