You can't do this natively. You have to grab the utxo set for your wallet from armoryd (
https://github.com/goatpig/armoryd/blob/master/armoryd.py#L439), then craft the unspent tx locally, which you can then send to armoryd for signing and broadcasting.
To craft the unsigned tx, you can rip the Armory python code into your local script. The logic is contained in a single file, albeit meshed in with GUI calls:
https://github.com/goatpig/BitcoinArmory/blob/master/ui/TxFrames.pyEdit: indeed, you other option would be to modify armoryd to take in a list of eligible addresses to get utxos from.