An alternative to your suggestion (which needs protocol level changes and is only useful to very few people) would be to have a very locked down system running an application which implements your requirements. Only your application is accessible over the network.

You could configure a lock-down time in the application and your "main" web application could send transaction requests to the system. When the system receives a transaction request the transaction would be executed after n (2) days you get notified (by e-mail?) and can interfere before that happens.
The key here is of course to have the system locked down as much as possible as it will have programmatic access to the private keys with your funds. Blocking all incoming ports and denying all incoming and outgoing traffic except that for your application  (possibly on a hardware firewall and on your system) and making your application secure enough shouldn't be that much of a challenge.
You could optionally run bitcoind on the system however that's a fairly complex bit of software performs many operations which could go wrong so it's probably better to not do that and to broadcast the signed transactions to the network in some other way (your outside application could poll it and then insert it into the network when it's appropiate).

Your locked down application therefore would need the following API functionality available over network:
- Create Transaction
- Cancel Transaction (you probably want to be able to do that over network)
- Poll created transactions