I mean, it'll work... the only absolutely positively essential things for a sump to function are the overflow drain and return. With what you have now and no modifications, you could place a heater and skimmer (although it is suggested that you're skimmer is in a chamber with a constant water level) and they would, for the most part, function properly. You could fashion your own filter sock holder and you'd be set. If you wanted to get fancy and run reactors or a refugium you'd have to get creative but it could work. It really all comes down to what you want your sump to do for you.
Now, having said all that, if you paid someone to set up your sump I'd ask when he's coming back to finish it.