What do the insides of the outer walls look like? If the stonework inside looks reasonable - I would think you are onto a winner.
I ask this since I’ve seen a few buildings in my Commune where exposing the stones has taken place.
One, had brickwork in a large area, rather than stones - presumably filling a gap/mending after damage - who knows. I do know that the builders had to remove the bricks/whatever and replace with stonework to match the rest. Not a problem, but is is an additional cost.
Another had more rough/odd cobbles than the big stones - in a couple of areas. Again, the answer was to remove and replace.
Our own house has an outer covering of something solid. The house itself dates back to 12thC and I like to think it is all good, solid, glorious stone blocks. The walls are 1+metre thick - but I am too nervous/impoverished to risk taking the outer shell off. It is impossible for us to judge from the inside, since it has been plastered etc over the years and to strip back inside and outside would cost more than I think it is worth…
If your would-be property has not been lived in - it might be in a raw state inside and easy to judge.
If you asking whether “pierre apparente” is worth it - I would say YES. Properly done it can be magnificent but does need to be done with regard for the “old ways” - not just stuffing cement in the gaps