I'm not so sure that 319's would be too big. It would be very unlikely that Flybe would configure them to seat 156 pax, 140 would be more like it, in which case they are only approx 25% larger but significantly more economical. If such an order is coming I would expect it to be in the region of 10 firm plus maybe 10 options.
Flybe are making an attempt to cover the middle ground between the likes of BA and BMI compared with Easyjet. Offering slightly more in terms of comfort for slightly more in terms of cost. Very similar to the old GO concept. Before I get my head cut off...I know that Flybe cannot be compared to GO in many ways yet..but they are on their way and becoming quite important in the industry at fighting the 'middle ground'.
I know for a fact that Flybe could certainly fill an extra 30 seats on many routes, in particular some of the summer routes into Spain would not be difficult...just look at the load factors they get out of EXT and SOU to AGP/ALC.
With regards pay....well i'm not so sure things will change greatly. I'm more under the impression that most of the crews simply want a more stable roster in many respects. Fewer changes and less roster turbulence. Yes pay is an issue but it isn't the most important factor for many.