You've already touched on the major points. Repack the bearings with good grease. Get plenty of brake cleaner, because the sticky snot stuff they use sucks. I like lucas heavy duty grease. It's rated for high speed wheel bearings.
On top of that, another popular mod is to get new tires a hair bigger. I think its 4.80x4 with a 4x4 lug pattern.
I moved up to a full on 8" tire, Kendas, from etrailer. Another very popular mod, but DO NOT USE HARBOR FREIGHT TIRES. They have stopped selling trailers because of the garbage tires they were including. I have enjoyed these kendas, and they track well;
AM3H200 Kenda 165/65-8 Bias Trailer Tire with 8" White Wheel - 4 on 4 - Load Range C
Another popular mod is to use eye bolts where the clamshell connects to the chassis. This will allow you to bungee down your stuff for transit. I did it, but I have mixed emotions about it.
Hope that helps, they are awesome little trailers once you upgrade them a little bit.