He got to be careful about weight distribution to. If he puts a cube in one and makes it take half the weight, then the stone it that specific area will be under a lot of stress, and probably break easier. He'll have to spread them around to evenly distribute the weight. And while it will make a golem move faster while still keeping the same mass, since the vector for all that weight displacement is directly up, downward vertical attacks may be blunted due to the conflicting forces.
I think it'll be most effective making a flying golem for reconnaissance. Or some sort of mobile floating fortress. Though the latter option seems like final boss territory.
My only problem with this are the unnecessary tournaments, I can't even call them arcs. They have no place in this manga, the people that like tournament arcs, like it when the arc is about the tournament and it's participants. In here, the battles are over in a matter of a few panels, most happen offscreen, there are 0 stakes involved, the tournaments serve literally no purpose at all. Even if you claim that the entire manga is pointless, there is progression, such as new villagers, new guests, additional villages, new buildings. But the tournaments halt what little progress is being made for no particular reason, and there's nothing to be gained from it.
Popular Reviews
I think it'll be most effective making a flying golem for reconnaissance. Or some sort of mobile floating fortress. Though the latter option seems like final boss territory.