Absolutely no reason to expect that joining Flybe as a first job puts any limitations on your future career with any other airline, except for the pure longhaul operators, who usually ask for 2500hrs+ on at least a medium jet.
Easyjet (and previously GB Airways), Monarch, BA, Aer Lingus, Jet2, BMIBaby, Flightline, Cityjet, Titan, and a variety of bizjet operators are all places that I know have taken former colleagues in Flybe in UK/Europe alone.