When removing a hard render from a 215mm solid wall, it may seem like a possibility that internal plasterworks would be affected (vibrations etc) but you'd be surprised to hear that it's not actually that likely. I'm talking from experience: we have taken an immense quantity of hard render off of solid wall properties in the past.
To take off hard render formulations like this you'd need no less than something like a 5 to 7.5 kilo Hilti. I know because these renders are ridiculously hard. These are completely against rendering Codes of Practice. Some brick face damage is inevitable in places when removing them but I can assure you that this is preferable to leaving on a render which is far too strong in formulation.
A hard render like this will continue to crack no matter what you do to 'spruce it up'. Thermal movement is going to happen and no material or cement render (and least of all a hard render) is going to stop it. A less-hardened 6:1:1 render (and less-hardened being the optimum word here) has reduced liability of material fracture when subject to stresses. Upon movement -expansion - the render will undergo plastic deformation, but due to increased properties of plasticity these non-reversible changes of shape will instead manifest as fine crazing occurring homogeneously throughout the material as opposed to outright fracture and surface fissures. Unless you're going to apply a flexible acrylic or silicone render topcoat over this hard render formulation, plastic deformation fractures will keep on coming through the new paint films you apply. It's simply a matter of time.
A surface scabbler is one option, as you've stated. And that's definitely not enjoyable work. But, again, your topcoat is going to need be a technologically advanced, flexible silicone render topcoat to have any chance of withstanding the stresses of plastic deformation on a cement render which has been made too hard in formulation.
I would forget about this "screwing on mesh" idea. I don't know where you got that idea from but please take my word that it will look great for about a week or so. It will end its relatively short lifespan in failure of epic proportion. Look for BBA Certified systems which are designed and certified for purpose. Mechanical fix and continuous bed adhesive EWI systems, for example, with fibreglass mesh reinforced polymer basecoat and silicone or acrylic render topcoat. There are many, many approved systems around.
The solution to durability and efficacy of external rendering lay in observing two main principles (understood hundreds of years ago and still universally understood and respected today by any rendering professional) : 1. Vapour permeability; and 2. Plasticity.
