Technically.....
Flybe have never flown from LCY. Their predecessor, the full service and loss making regional carrier Jersey European Airways did.
The current flybe business model isn't a great match for LCY so taking on Cityjet would entail running two carriers with two different business models. Then throw in ScotAirways and VLM into the mix and you have four ingredients. We could make it five if you took the previous post about folding KLM Cityhopper in there as well.