could we just merge our sub weapons as one thing, being out kutum and nouver or nouver and Black Star sub hand instead of just switching back and forth, it could be in the process like we buy them separately as we do know but a third item can be introduce that would allow us to combine them, just like the normal vell and a separate item being the bless to make Blessed vell heart. it could be a cause where nouver itself is still more ap than when merged vice versa kutum is more dp when merged buy maybe 5ap/5dp. or would this be too much of a game changer?

No because that breaks damage reduction and evasion passives for classes.

On the contrary we need more variety.

Agreed, I want an accuracy offhand with 2 crystal slots. 

Accuracy offhand already have all special attack damage increase instead of the second crystal slot so that's actually better.

You will probably have to wait for the Fallen God/Labreska tier offhand to be introduced which will most likely be a merge between Nouver and Kutum stats like the Labreska helmet is a merge of the Griffon/Giath.

Given they already do split for the shoes and gloves mostlikely they will for subs aswell.