You don't need to download the blockchain to generate a wallet, you can always create the transaction on an online computer then transfer it using a usb the offline computer, sign and use online computer to broadcast it.
Bitcoin Armory can't sign normal raw TX. I don't know if there is any script which can do it. You can use CounterWallet to create a Armory compatible raw unsigned TX.
How about bitcoin core ? We need to download the blockchain or no?
Yes, you have to but you can also use Bitcoin core like ranochigo told. You might be interested in
https://bitcointalk.org/index.php?topic=958960.0 but I haven't verified the source code yet.
-MZ