I think - olof + hallzerk is a pretty good fix by itself. Bring in that main awper to the team again, especially with krieg nerf. Or Jkaem if they want to go without main awp'er.
Hower, if they were to get Niko off IGL, I would do - olof and broky, and maybe try to get nexa and Niko's cousin. Or even Hallzerk + Tabsen IGL or something.
That said I think Niko is doing pretty well as IGL. They have brought some interested stategies to the games lately. Not just running and popping heads like they used to. And also not boing AF like many other teams just playing slow and methodical.