I once created a hero based on a foot soldier. The experience was negative: it was too small, and hard to see. Either this model needs to be made about one and a half times larger, or a larger model should be used from the start, or a mount should be used: one of these options would be highly desirable.

But why is a huge hero needed (the Overlord sends his regards)? Moreover, there is always an aura around the hero that reflects the faction he belongs to, so you can't "make him invisible" anyway, and you would have to be blind not to notice the hero. Besides, there is Biara, who isn't much larger in size, but the developers didn't think that a "not very large" hero was a bad thing, so I don't see anything wrong with this. Increasing the size a little would be nice, but no more than that. It's better for the hero to be on foot and not the size of half a mountain, but still be present in the game. Also, heroes on horseback aren't that big (without the horses themselves), so a small hero size would be quite logical. Besides, you yourself wrote that the hero's appearance isn't that important to you, so what's the problem? Or maybe it's better to struggle with the geometry and connect the mount, the rider, and the animation of shooting a bow from a third object. In my opinion, these are some unfounded stereotypes about heroes not being as large as a Castle. If we talk about the hero suggested by the lady above, I can share a few variations of textures for this hero, so you can have a more accurate idea of what needs to be done. The textures are not based on creeps/heroes from this game, but they will provide a more than illustrative example.