Can a Eurofighter 2000 trainer be converted to a combat capable Eurofighter 2000?
From the Wikipedia page on the Eurofighter Typhoon, under Variants:


  The Eurofighter is produced in single-seat and twin-seat variants. The twin-seat variant is not used operationally, but only for training, though it is combat capable.


No source is cited for that claim, but it seems logical enough.