To be honest I'd be a fan of more of these types of deals, loans with an option to buy. There's plenty of players who don't work out at one club but do another, Gomes has been utter wank for Barca and didn't impress at the Euro's really either, but was highly-rated at Valencia and there is clearly a talented player in there somewhere.
If he does shit, you're not liable for him beyond the next 6 months. If he's good, you have the option on the table that can't be retracted in the wake of any good form by his parent club to make it long-term.