Felix for £45 million is a gamble but could be a good deal for Chelsea. There's still potentially a top player there somewhere, he's costing them £9m a season with wages and they're banking the entire Gallagher fee. Helps them a lot this year but adds another £9m for the next 4 years after this. If he's even a moderate success, selling Felix for anything over £35m next summer or £25m the following year should be fairly realistic. It's a much more sensible deal than some of their recent signings.
With their first team academy graduates running thin now, they already have to be thinking about who they can sell next summer and likely the summer after to help them, I can see him being a decent flip.