To me, one of the best production bowie knives ever made is the Cold Steel Bush Ranger in Carbon V. It's far thinner, lighter, and more generally useful to my needs than the CS Trailmaster. I'm particularly fond of 'bowie' knives made thin and light like the originals. The big thick ones have their place, but for real world carry on hikes and hunts, the light, wide, thin ones get carried while the big thick ones get left behind.
If you're interested there's quite a thread on bowies going on over in rec.knives. The poster called Chas is an interesting one to read. He's not only largely historically accurate, but apparently has some good knowledge about fighting qualities of knives. Me, I wouldn't know much about that aspect. My knowledge of knives is strictly limited to things I've experienced and knife fighting isn't one I hope to ever experience.
For me, in my real world use of camping, hunting and fishing, the ideal bowie is one that bridges the gap between folders and machetes, or between small fixed hunters or filet knives and bowsaws. To me, the bowie knife should have a blade between 6-9" and not be over 1/4" spine thickness. It should be so easy to carry that it causes no concern, should be useful as a kitchen knife for camp and kitchen, should be useful for hacking through undergrowth and brush, and should be a stellar defensive knife, should that need arise. In a word, my choice in bowie knives is just about exactly as the original bowies. Nothing fancy, just a good workhorse knife that also happens to be a good fighter. (or so I've read)
Now I realize that I've just outlined a knife, and a selection of uses that are quite different from what you may have had in mind, but to me, they are the requirements for a 'Bowie' knife. To me, a bowie knife that's too big to comfortably carry when needed, is just too darn big to be really considered. Actually, one could make the argument that in today's world much of any "bowie" shape is too darned big to carry for any but the most remote outings, and I'd not disagree. Still, I have a fondness for the original shape and design.
Your q of the relevance or place of the bowie knife in the modern world is a good one. There's almost nothing camp-wise that a good bowie can do that a good folder combined with a small machete can't do better. The one possible exception is that a good bowie combines defensive use with utilitarian at the price of some compromises. From what I can tell almost all of the compromises are on the utilitarian side, not the defensive side. In fact, a good thin bowie would be one of my first cutlery choices in a defensive knife.