I don't much care for the tires, either, but for less than a ton of hauling they should be fine. You can put bigger ones on there up to a certain point. It looks like the hubs have four studs, and that fender will have to come off if you go much bigger. My only other concern is that there appear to be two jacks behind the wheels, but none at the tongue. That's not necessarily a sticking point, as anybody with sense enough to pour sand out of a boot can bolt on a jack at the tongue, but I would want to have all three. Actually, I might be inclined to put it at the front end of the frame rather than on the tongue, if that didn't interfere with cargo space. That way you could just jack it up and leave it somewhere if you wanted to.
I think it's a decent trailer, but I would do a good bit of research before buying it. Shop around and see if you can find one that meets your expectations out of the box. If not, check the local welding shops for trailers. Every shop I have ever seen has at least three trailers sitting out back waiting for a buyer. They can also probably build you a custom trailer with everything you want for little more than this one. If you come up with nothing going those routes, buy this one and modify it to your needs.