Dovecot CalDAV server

I've been once in a while over the years thinking about implementing CalDAV (and CardDAV) to Dovecot. It might be time to start that soon. Does anyone have any suggestions? So far my main goals would be:

• scalable, of course
• configurable storage (object storage, regular fs, maybe some key-value dbs, maybe storing as emails)
• efficient indexes (potentially using key-value dbs? or maybe just local files. not sure yet what kind of indexing is needed)
• have it work with dsync (= replication & migration)

Some things I wonder about:

• Maybe there is already some code out there that could be used to implement it faster?
• Maybe even use something else besides C to implement it.. Then again that makes integration to Dovecot more difficult.
• Is anybody interested in helping to develop this? :) I think I still have too much other work that I won't spend a lot of time coding it..

One thing that makes this easier is that Open-Xchange has already implemented a CalDAV server, so they can help to avoid the biggest design mistakes. (There are a couple of reasons why they'd want to replace that.)