Its actually weird that ssj4 is called ssj4.
The 4 doesnt make much sense.
To become ssj4 you need:
1. Being able to become a ssj.
2. The conditions to become Oozaru.
3. Becoming conscious, in control, over the Oozaru form
4. Combining the 3 points above.
Basically a ssj1 can go ssj4.
You never need to have been ssj2 or ssj3 in your life to become ssj4.
As its sorta Oozaru and ssj combined in human form.
Therefore the #4 in ssj4 doesnt make much sense.
What could be a better name for ssj4?
Super Saiyan God. - Oh wait...
Seriously though, maybe like Primal Saiyan? Or Primal Super Saiyan God? I really do hope they re-introduce the form as canon in some way, shape, or form. I thought it was great, always did.
Honestly, I think Primal Super Saiyan God could make a lot of sense. With the introduction of Super Saiyan God it feels a little like Goku and Vegeta have diverged heavily from what Saiyan's once were, they're now more like Gods than Saiyan's and I think the re-introduction of Oozaru concepts and going back to the roots of Saiyan heritage could be a good route to follow. It also links in with the whole blast from the past shit going on recently, like the reappearance of Kaoiken.
Also, Oozaru made a Saiyan go madly out of control in return for great power.
SSG is about a calm and powerful Ki.
Combine the two and you get???
Then you could up it again with Golden Oozaru and get a Super Saiyan Primal Super Saiyan God. Toriyama seems to love mouthful transformations nowadays, so that should be right up his alley.