I don't like them. Seems like too much work for too little pay off. I also don't think you can really call them, "realistic", either. From a "realism" point of view, as written Halfings would be completely useless in combat. They're much too small and have very little mass. Which means they can't lift much or put much force in the blow.
OTOH, normal weapons simply sized for giants would be almost unliftable, even by giants. Certainly impossible to actually use in combat. While you can handwave the existance of giants by saying "magic", their strength in D&D really isn't large enough to wield weapons. Because the mass of things basically goes up exponentially as they double in size. Is something twice as big, twice as heavy? No,it's 4 times as heavy. You also have to factor in material strength and things like that.
I think actual giants and halfings would have their own unique weapons, rather than simply mimicking human ones. Halfings for instance would probably go with pointy weapons, like a stiletto. Since the only way they could possibly hurt someone is if they pack all their force in a little area.
Giants would have things harder. They would want to take advantage of their reach and long arms, but they would have to be thin, to keep things light. But at the same time, that would result in lots of breakage.
So actually, I think they probably would just use human sized weapons. Because there is a reason that the various weapons are the size they are. Not just who wields them, but the way newtonian physics works.