If your cousin is going to be using the pen at university, a screw cap is definitely a good idea, but most of the pens I've seen with one have an internal reservoir, which will be a bit less convenient for him than a cartridge pen would.
Given that, the Kaweco Sport is a very good call. The Shaeffer No Nonsense would be ideal, but is tricky to get hold of these days. Most of the vintage ones on fleabay that are halfway affordable have a calligraphy nib, and the more recent models (which may well be knockoffs having nothing to do with Sheaffer) have a slip cap rather than a screw one.
Another plus for the Sport is that if he uses it clipless it'll work very handily as a pocket pen, and you can get short international cartridges pretty much everywhere you go in looking for a notebook or an A4 pad. They're also (in my experience: your mileage may vary, of course) pretty reliable.