As suggested by the previous poster, 2x daily on weekdays and x daily at the weekend (Saturday morning and Sunday evening) would make sense. With 6K passengers (with further growth over time) a daily service to LCY is very sustainable.
Just like to comment on a point made by a bannercounty on building the airport in the Midleton area. An independent report advised against an airport in the Midleton area (Ahanesk) as the "runways would be severe as the ground is undulating, and that the approaches from the north and north-east, which pass over a range of hills attaining a height of 600 feet, would frequently be hazardous in the weather conditions prevalent in the area".
Dáil Éireann - 09/Nov/1955 Ceisteanna?Questions. Oral Answers. - Cork Airport
Finding the perfect airport location in the Cork area (including Midleton - East Cork) is difficult due to its topography (beauty), so the Ballygarven site (current) at the top (not the side of fortunately
) of the Lee Valley on a relatively flat surface is a reasonable alternative in these circumstances. A low lying airport would have been preferable (with more favourable meteorological conditions), but very difficult to achieve with so many surrounding hills.
You could have gone further out away from the Cork metro area for the absolute perfect airport site (North Cork possibly), but having your airport located as close by to a densely populated area I think is critical. If you look at how Shannon airport for example has struggled since the stop-over ceased (numbers plummeted and is still struggling), built basically in an isolated, relatively unpopulated area but on a very good airport site. Shannon airport will always struggle to be viable unfortunately (without government support) due to its location away from a reasonable population base.