Blair wouldn't try to be strong and effective. He'd try to be strong, he'd be a disaster, and he'd totally discredit the institution. But just his mere appointment would be a PR mistake for the EU as a whole.
Just look at what he's done as Quartet Envoy to the Middle East. The peak-to-trough part of the business cycle is an outlier. Carnot would have died laughing.
Blair wouldn't try to be strong and effective