Tolgayurdal, thank you for your time. I'll try to answer all your questions as best as possible.
The Blues replacing Morwe and Herumor would allow for Alatar to be a hero killer (I mean he is like Aragorn, a ranger/hunter with magical skills. In fact, I was shocked you didn't give him a bow weapon).
As for Pallando, he could be the mass slayer, or hero killer since he is of Namo's people. Either Blue Wizards role can be tweaked to fill in the gap of Morwe and Herumor.
In regards to light vs dark side--I guess Alatar could be on the light side since his nickname is (darkness slayer). But whichever side, the Blues can be on either one. But don't forget that canonically both fell from their appointed task which brings me to their ring-hero mechanics.
I feel if Alatar picks up the One Ring, he would become the new "Dark Hunter" a throwback to the Elder Days when Melkor utilized the Dark Hunter to hunt elves. This would be unique because we would have a ring-hero with a Bow for the first time.
I also thought about Pallando's ring hero mechanic and realized that he would be greedy as well and use the power of the ring for his own ends. Thus he could become a spirit master (or Necromancer)--creating wights, ghosts, etc.
Thus, the only good outcome for Dorwinion finding the Ring would lie in the King of Dorwinion who would summon the counselor as you described perfectly.
Whoo, got through a lot here, but on to your last question: "The other subject is Entwives, they can be natural ultimate spell but would not it too much similar Rohan and Lothlorien spellbooks? Plus it doesn't sound for fitting dark side, does more close to Avari, i think."
In regards to the Entwives, I wanted to share this link:
http://tolkiengateway.net/wiki/EntwivesIt states on here that some survived and went to the East while some may have been enslaved. This is why I felt they could be used for both. The Dark side Enslaves the Entwives, the Light side allies with them.
I hope this answered everything. I know this won't be implemented for a long time (if ever) but these are my suggestions and I think they have a very canonical "ring" to it. Take care and thanks for the discussions as always.