Old render repairs on brickwork

[klb]

I am in the process of getting some quotes for re-rendering of our 150 year old cottage. Someone has suggested only knocking off damaged or cracked areas such as patches that sound hollow. After patching up, all the render, old and repaired areas would be cover in a Tyrolean finish. I am told by the same guy that it would be unwise to knock all of the render off and completely renew the lot, as it could damage the brickwork beneath.
This job is being paid for by a neighbour ( a long story ) and this particular tradesman is one of his contractors.

I am reluctant to agree to this type of repair if later on we have further problems with the old render which is left on. I wonder if the tradesman is looking to keep the job/cost to a minimum on behalf of the neighbour.

Would it be safer to re-render the lot or is this type of repair suitable?