The big issue with steerer/stem extenders is the added leverage the higher placement of the bars will exert on the top end of the steerer. This is why most carbon fork instructions restrict the use of them.

But a second issue is the added "joint/connection" between the stem and the steerer. We see so many bikes with loose stem pinch/wedge bolts with the OEM stem/steerer already. Please periodically check the various fasteners for remaining tight (in addition to any steerer cracking).

I would first explore the shape of the bars and the rise angle and reach of the stem before suggesting a riser. And, yes,, generally some or all of the control cables will need lengthening. Andy