As always, Shed makes a very good point. Unlike the CX service which is likely to add 'new' passengers for MAN (see discussion on another forum), more flights to the likes of Malaga, Palma and Faro would probably lead to a redistribution and thinning of passengers on existing carriers rather than create extra business. However, it is not always easy to judge when that saturation point is reached, especially if there is a climate of optimism and overall market growth and not just at MAN. (Is that the case now - not sure?).
Perhaps BCN & MAD are slightly different in that they should be attracting an element of business traffic where timings and/or frequency may also count.
I wasn't aware of Ryanair's plans for 10 x weekly to MAD. I thought it was 4 increasing to 5 or possibly 6, but I well may be out of touch.