Dry-lining on external cavity wall w/ existing full fill insulation

Due to an unrelated structural issue, we've had cracking on external walls near the ceiling upstairs. As part of the remedial works, we'll be applying slabs over the existing sand+cement internal plaster finish to cover the existing cracks. Each of the 4 rooms affected upstairs has a gable wall with no windows/rads and a non-gable wall that has both windows and rads. The cavity wall is already full-filled with 150mm Cavitytherm boards.
To apply even the thinnest insulated slabs to the non-gable walls, we'd have to remove the existing plaster reveals, adjust the radiator plumbing, and get new window boards. None of that headache applies if doing the gable walls only (which represent between 40-50% of the external wall surface area of each room). We'd be using standard plaster-board on the non-gable walls.
My question is, is it worth doing the gable walls only in insulated slabs?