It is module system only related problem. But editing txt u can set item weight arbitrary high (i mean very high 'cause anything is limited in computing, but high enough to any normal purposes).
I've never tested, but probably it is even possible to make helium balloons -- items with negative weight that increase speed of traveling. lol, items with negative weight don't increase speed, they work much funny.
Btw, there is a number of such limitations, for instance, same with troops attributes.