What's the use of layering or splits if the keyboard can only produce a single type of sound at the same time (mono-timbral)? The Electro line doesn't have enough 'horse power' to make more than one type of sound at the same time, it is not designed to do that.
As for pitch + modwheel; why not include aftertouch, which the Electro line also doesn't have?
If you add more controller features to the Electro and make it multi-timbral (= it can produce multiple different sounds at the same time), you pretty much end up with the Stage. Sure, it adds some additional stuff like more memory, more effects and morphing but it's pretty much the Electro's big, grown-up brother.
In my opinion the Stage line is the full-featured product, while the Electro and Piano lines are slimmed down versions catering either for musicians who want a light rig (Electro, though the Stage with semi-weighted keys isn't that heavy either) or who don't need the controller/synth/organ features of the Stage but who do need a good weighted keybed for playing pianos.
Personally I think the complexity of the Stage (regardless of which version) isn't that bad. Sure, it has a lot more knobs and buttons and it can seem daunting at first, but you don't need to use (let alone understand) every single knob/button to get good sound and have fun.
At almost twice as expensive as the Nord Piano 2 or Electro 4 HP, the Stage 2 isn't cheap; none of the Nords are. If you however compare it to the Electro/Piano and see what additional stuff you get for that money (more memory, two of each section and you can use all of them at the same time, more effects), it looks pretty good I think. A Stage 2 certainly lets you do more than two Nord Electros or Nord Pianos would allow you to do. If you need a second keyboard, just add a MIDI controller (like the organ version of the Fatar VMK-176, which has waterfall-style keys like the Electro 3/4 or Stage 2 SW73).
Just my opinion. I can understand why you'd want additional features in the Electro, but I think that keyboard already exists. You'd need to spend quite a bit more though.