How can I generate wallet files for multibit or armory?
For MultiBit you could use the command line utility called WalletTool that Mike Hearn wrote. You can use it to create bitcoinj wallets (which is what MultiBit uses). 
There is a description of it here:
https://bitcointalk.org/index.php?topic=43616.msg1451177#msg1451177

You could wrap calls to it in your favourite scripting tool fairly easily I imagine.