is archive_lag_target what you are after (force a switch every x seconds)
Is my memory fading me, but is there not a parameter the will (specifically) force a redo log(s) to be archived.
I thought LOG_CHECKPOINT_INTERVAL or LOG_CHECKPOINT_TIMEOUT did that, but as I re-read these parameters definitions they seem to only control the checkpoints which my indirectly effect log switches the thus archiving...maybe not?