Is this possible, or does immigration insist on validity of at least 12 months...

You can do it but the new extension won't be for 12 months; rather it will only be until the expiration date of your passport.

As said the extension will only be done up to the date your passport expires. Then you will have to apply for new extension when the shortened extension expires.

As stated above they will only give you until the end of passport. After recieving new passport go in and get stamps transfered to new passport and befor expiration date of extension of stay go in for new extension. My extension normally expired in Feb. but because passport it expired in Dec of 2014. I preformed the preceding functions and now have a new passport with my extension of stay.

As stated above they will only give you until the end of passport. After recieving new passport go in and get stamps transfered to new passport and befor expiration date of extension of stay go in for new extension. My extension normally expired in Feb. but because passport it expired in Dec of 2014. I preformed the preceding functions and now have a new passport with my extension of stay.

But just to clarify, they won't add on the "missing" month when you transfer stamps to a new passport. The extension will still need to be renewed 11 months after the one issued in the old passport.

As said you will only get around 11 months extension.

You will then have to apply again for 12 months when you get your new passport.