Re: mapping coinjoins, I assume you mean logging which inputs match with which outputs. This doesn't need an anti-incentive to prevent, you can simply make it so it isn't possible to log through the use of blind signatures.
I think DarkSend does not implement blind sigs because they didn't work when DOS'ed (?) or something to that effect:
https://bitcointalk.org/index.php?topic=421615.msg6001085#msg6001085...and, again, if I remember correctly the solution was one where the node knows what is being transacted.
(note: I'm no coder or cryptography expert, so I'm going with my understanding of past discussions I've read - some of which may be inaccurate).
Re: Bitcoin foundation, they aren't involved with this decision. All it takes is one person to implement it and upload the implementation

That's unsettling for Bitcoin's stability

It's like the opposite end of bureaucracy (=>anarchy)
Re: delaying payments, no, it isn't possible to have consensus that way. You can check yourself, but anyone that's offline will need to trust someone. This means if the party they trust lies, consensus is broken.
Hm...
edit: check this too
https://bitcointalk.org/index.php?topic=421615.msg6003693#msg6003693