Never thought about an air line... what are the benefits? My automation box will monitor PH and EC.You could probably get away with massage jets in all return locations - you will just need to monitor your pH and adjust accordingly as the pH will rise with increased aeration. Are you planning for an air line with or without a blower also?
My understanding of massage jets is that the inside orifice can be changed out for different sizes to give the desired affect. Maybe another member will weigh in with more info on them.