Single password for all encrypted partitions

Hello,

I encrypted several partitions at install time with the alternate CD of 10.10. However, I need to type a password for each at boot time.
There is no way to use it properly encrypting a PV for lvm since if you add a disk, you'll need to encrypt the other PV and so it will also lead to 2 passwords. And if you encrypt the partitions inside a vg, you'll need several passwords.
I even thought of creating a raid0 array to encrypt, but it become quite heavy.
ANd no way to encrypt a lvm volume group since no /dev/xxx device exists, just the LV.

I saw that Opensuse & Fedora have an agent that includes in the initrd which, I believe, tries the first pass for all the partitions and doesn't ask for the others if it works, or decrypts a wallet including the passwords for all partitions.

I did not find it in Ubuntu.
I may be paranoid but I think that would allow anyone to use encrypted partitions.
Is it scheduled by default for natty, or does it exist as a package to install ?
Why not add this in the desktop installer ?

Thanks you
Bye