This is actually a very neat question. What are we trying to do? Well that depends. Everyone joins the community for a different reason. SSCBen pretty much hit the nail on the head when it comes to the three main "branches" of the hobby. I definitely lean the most towards the "warfare" part of water warfare, so my response will definitely be slanted in that direction.
So for me it does not matter what kinds of blasters are being used on the field, as long as my team has better ones than our opponents, haha. (Or more specifically, ones that my teammates can use most effectively in the given situation.) I'm a water warrior because I enjoy strategizing for days in advance, planning out the best way to defeat the enemy. I enjoy stalking through wild battlefields while every nerve in my body is alive. I enjoy leading my team through difficult situations and overcoming obstacles. I enjoy the heat of battle, and the physically-demanding nature of such a close-quarters game. I enjoy the small-scale tactics employed during the battle and having to think fast. I never really thought of trying to make water wars "realistic" like real wars. In some ways yes, like creating battle scenarios that one might find in real warfare, but I definitely recognize that water guns are nothing like real guns, so tactics are often very different. For example, this is the only game where barricades (such as mobstacles) and other low pieces of cover are useless except perhaps as a way to avoid being seen. I don't know anyone who plays water wars to have a realistic war experience. Airsoft or some types of paintball are way better for that. Water warfare is more "sporty" if that makes sense, namely in the mechanics of straight-up combat. To put it simply, the gametype/scenario can be very war-like, but as far as the actual act of fighting goes, it's much more like a sport.
The point of all that was basically to say that, even if every single person on the battlefield is using a copy of the same blaster, I would still have fun. Even if there is no variability in the weaponry, there is always tons of variability in the battle. Water warriors fight on a larger variety of battlefields than any other game as far as I know. Schoolyards, backyards, forests, swamps, lakes, abandoned factories, and even caves. I realize most people aren't that crazy, but even so, the battle conditions are always different. People have different skill levels, and will try different tactics each time. Think about a sport that you enjoy watching, whether it be baseball, football, hockey, etc. Those games are always played with the exact same rules and equipment, but each game is unique. Water wars are like that, but even more exciting because the setup can change each time, and there's a lot more freedom than conventional sports.
That's my answer to the title question, heavily fueled by like twenty wars worth of experience. But I realize that's also rather biased, and that some people are more into just collecting guns and messing around with them. In which case, I don't really see why it matters that X gun is better than Y gun. If you don't care about being competitive, than go ahead and use that Hydroblade. If you do care about being competitive, you'll quickly find that the blasters are only a small part of the equation. Also I'd like to point out that water warfare is probably the only wargame where there really isn't
that wide a gap between the worst guns and the best ones. Case in point, if you tried to bring a stock Nerf Longshot to a NIC war, you would not stand a chance against everyone with their homemade contraptions that shoot darts almost too fast to see. However I have gone toe-to-toe with big CPS while only using guns like the XP 270, and while difficult, was not impossible. You can be competitive using almost anything short of like an Electrostorm or something.
As far as innovating and making new types of homemades and stuff, I think the only thing stopping that is the fact that there are so few actives left. There hasn't even been a community war in like two years or something. I can't speak for anyone else, but for me it's mainly being busy with work and school, and trying to focus on other things. Which is fine, but nobody new is really stepping in. So if you want awesome homemades, you better get busy because I don't think anyone else will do it. I hope to someday come back and get into that stuff again, but it'll be some time.
Sidenote: WBLs can work, just not necessarily in the way most people might think. It's very hard to get a hit with one, but there's one thing they do better than any other weapon on the field, and that would be intimidation. CPS 2000? Monster XL? Forget about them; NOTHING is scarier than seeing a 3" PVC barrel leveled at you during a battle. Until it is fired, the user is effectively invincible and can influence the enemy team in all sorts of ways.
You see the same problem of people viewing the "point" of the hobby narrowly in Nerf. As far as I'm aware NerfHaven still filters the word sniper to loser because "There are no snipers in Nerf". Well, as you point out, there are tons of people who want to be snipers.
Bahaha, that is the most NIC thing I've ever heard. We should filter the word "nerfer" to loser on this board, hahaha. But seriously, I remember arguments over using the term sniping even here. The more I think about it, the dumber it sounds. If you hide in a tree and pop someone beneath you, I see no reason why you couldn't call that sniping. I don't think it has to be the same percentage of combat distance as real warfare or whatever the hell people were trying to use as an argument. The official definition of the word "sniping" is actually pretty ambiguous. According to Google:
the action of shooting at someone from a hiding place, especially accurately and at long range
"Especially", not "necessarily". Plus I think being in a tree or other hidden vantage point would give you pretty long range anyway, at least compared to everyone else. "But oh no, it's not the same ratio of regular range to sniper range as a real war, so we won't have any idea what you're talking about when you say sniping!" Like, how do you even communicate at all?
Nerfers crack me up.
So with that said, if you want to actually make a sniper water gun, go right ahead. I would actually put the CPS 2000 in that category already, since the best way to fight with one is basically to sneak around the fringe of the battle and only take shots when you have a good chance of connecting. You can call this "sharpshooting", but to me it's the same damn thing. Basically what you're looking for when designing a sniper is something with high range/output, but low shot time because you'd want the blaster to be smaller and easy to hide with. A big 100' cannon would give you the range, but you wouldn't be able to sneak around very well with it. A WBL would have even better range, but they're also cumbersome, and also inaccurate. Note that just like with real guns, you can snipe with anything, it just might not be ideal for it.
Wow, I haven't made a post this long in a while. But hey, my semester's over and I have some time to breathe now. Definitely miss this hobby. I'll have to see if I can get back into the game at some point. Water wars are great for "social distancing" because nobody wants to come within like 40' of anyone else, haha.