Well, here's my wildly subjective take on a "Dream RtW3". First and foremost: I am very much ready to take RtW2 as it is and play the heck out of it, as such, nor do I mean any disrespect towards the fantastic work that lead to RtW2, nor do I feel entitlement. With that out of the way...
Missiles? No. Sailships? No. Helicopters? Nah. Ironclads? Not really. My main gripe is not what's missing "from outside", but what's missing "from inside".
To put it simply, imagine something along the line of Victory at Sea: Pacific, except a game that actually works. Admittedly, this would take a huge effort, because this miiiight not work too well with a turn-based strategic campaign, but who knows, maybe it does. Anyway, I like to think that earlier ideas of something along these lines are already presented in RtW1, looking at the "XY has only 50% fuel remaining" and such, as maybe a remnant of an idea that never came into fruition then.
The exact nature of my dream is not completely clear, how much micromanagement would be needed from the player to put together convoys, patrols, what would generate VP-s, how could the AI handle all this, et cetera - again: I am fully aware that this apple is too big to chew. Still, in theory...
- You could for example, "draw" minefields on the map, that mining would be then carried out by your minelayers IF... (a multitude of if-s), or you could place fortifications to exact positions on the map, so it's not "have a random battery somewhere in the country".
- You could create squadrons, task forces, organizational decisions. You could build your own "famous" or accomplished formations, or define a rule for example that no capital ship can sortie without two or three specialized ASW destroyer escorting it. Or let's say, AA cruisers. You could still be in trouble due to malfunctions, oil shortage etc. that would force you in some way in more cases than not to not play by your book, but using specialized designs according to their role could be the rule, not the exception depending on random selection. Would you still select a machinery tuned for "speed" for your battleship, if you intend her to be the sole capital ship of your XY task force rather than a randomly selected participant in a given sea region...?
- You could actually support landings and if it fails, you lose assets, you lose equipment, boats, ships, marines, fuel, time, whatever really, and maybe with them the ability to launch a landing in the first place until rebuilding.
- Things like "Range" or "Speed" would or could play a dividence on the strategic map. Again: not saying that they are useless now, but they would certainly get a new role.
- You could specialize aircraft and ships alike, and make sure they will do what they are intended doing. Having different land-based and carrier-based craft would have a point.
- Strategic reconnaissance and intelligence could be a huge asset. Right now a lot of the scenarios - for a good reason - starts esentially with the contact itself, then you can get a clearer picture and if you can, you may chose to disengage. In this iteration however, IF you put the money and effort in, you can be far more picky about this without the "Oh, nope!" moments, but that money or those airplanes will be missed somewhere else.
I do not continue for now, but I'll say that I can clearly see why someone would NOT want to do such things. Currently, RTW is about designing ships and throwing them into the fray, with a fairly abstracted, but actually rather clever system that somewhat connects the two and generates scenarios for them. Going down "my" route would divert more attention to the war itself, and screwing around with patrol lanes, convoys, landings, underway replenishment, base and resource management is certainly not everyone's favourite.
Still, I'd rather see the above than an extension of the timeline, even though I am very much aware of the insane amount of effort and resources needed to realize this, and for this reason it is highly unlikely that I'll see that before I'll see a helicopter in the game. Pprobably the AI would be the biggest daunting issue.
Yet, a man can dream.
When it comes to realistic expectations? Better night battles. I am aware that radar will be a thing, but still, some visual representation and effect of muzzle flash, burning ships, searchlights, night recon airplanes dropping illumination shells - something along these lines. Right now in RtW1 it is maybe possible to start a scenario with getting high-caliber shells (not torpedoes!) into your face immediately without the idea of where they are coming, let alone who is shooting. Basically, right now night battle = day battle - acquisition range.