Ndombele plays as the most advanced midfielder in our formation, calling it #8.5 or #10 is semantics. The deeper roles are played by PEH and Sissoko/Winks.
Playing GLC upfront will push Ndombele backwards. You can't play a #10 and keep Ndombele in his current role, while having your LB and RB push up. Doing that against any decent team is asking to be shafted.
To play GLC and Ndombele together will require a totally different formation and tactics, for which you might as well hire a different manager.
Sissoko does not just babysit the RB, but it is part of the job in his role. Who ever plays that role, even if its Ndombele or Kane, will have the same responsibilities. The position dictates the responsibilities, not the player.
Until there is better player for the role, the job will belong to Sissoko/Winks, as they are the best options we have fore the role in the squad