A seat for every pax is a lovely idea, but not practical at all I'm afraid. Airlines can't strap in a rear facing carseat which small infants use until around the 9months of age mark. Best thing would probably be a Parent wore a sling with said infant in.
Of course you also get the parent who comes all tooled up with their five point harness, CE marked, forward facing carseat, seat bought and then told they can't use said seat onboard. Very frustrating.