TUI don't own Coventry airport, they only have the lease of Coventry Airport (& I think Air Atlantic lease their bit of the airport)
Thomsonfly serve mainly big sunshine destination airports which Ryanair steer clear of so I honestly think that if RYR began flights from CVT, these would compliment Thomsonflys routes (& would possibly poach passengers from EMA & B'ham rather than Thomsonfly passengers). I was just using Ryanair as one example of an airline Coventry could try & attract, they previously operated from Coventry (in the days if the 1-11).
Also, it has been mentioned elsewhere that if TUI win the planning application, they may well look at selling the lease of Coventry & go back to just operating aircarft from there, would many people be willing to buy if Thomsonfly were the only (regular) passenger operator along with Atlantic & Emerald on the freight side (around 20 movements a day, not a large amount to pay landing fees, for ATC, etc.. & only around half of them bringing passengers in).
FC