Jim French has said that they are looking at carriers which are
'digestible, rather than transformational' and a
'bridgehead into Europe'
Flybe Pursuing Two Purchases as It Seeks to Build European Bases, CEO Says - Bloomberg
Cityjet would be very challenging to 'digest' for the reasons already mentioned here, and others, and would be mainly a further chunk of UK and Irish market share rather than a bridgehead to anywhere.
I don't think it could be sensibly considered to meet either of Jim French's criteria.