I don't have sufficient knowledge of the codebase to write up a full blown proposal, but since GSoC is sponsored by google and for KDE, wouldn't this be a perfect project for it? I seen where akondi devs have talked about GCal support, but I haven't seen anything come of it. Full co-operation between kontact and Google apps would be a dream come true -- When I'm forced to use a non-linux box, I could just open up google and everything I need would be there -- from email to calendars to rss feeds. If only GCal supported "Todo"'s.... I suppose the only problem here is if this project would be doable in the constraints of GSoC.
Comment by krake: This is already being worked on here.
Shouldn't this SoC be based on porting the composer to be based off of WebKit/KHTML with contentEdtiable? It is the only way KMail is ever going to properly support rich email creation. The current composer is about 5 years behind the times in capabilities because it is based off of QRichTextEdit.