How are all of you making statements about how hard or easy it would be to do, without knowing how thick the clear coat is to start with? We all know that modern clear coats seem to be getting thinner and thinner and whilst it is 'normal' for me to see around 150µ total paint thickness on most new VW's, there are other manufacturers where the film build is like 70µ out the factory... so it is a very 'unsafe' assumption to make that because its a new modern car, you have a certain clear coat thickness/life in the paint.
And even if you do own a PTG, its not a foolproof solution (unless you are dropping serious money on one which measures individual layers) because even though the total film build may be high (like with most repaints) you won't always know what each individual layer is doing.
If there is only a few microns of clear left, it will be super easy to strike through - I have a BMW bonnet in my garage that I use for testing and I struck through the clear in a section reading 250 odd microns - presumable there was a little clear on top of a bunch of primer/base/old paint? There are also sections on the same bonnet where I have sanded extensively and am picking up readings as low as 210µ and the clear is still in tact.
IMO the best advice I can give is
a) make sure you own a PTG if you are planning on doing any serious correction work (any more than say a finishing polish)
b) always perform a test spot to enable you to remove as little paint as possible whilst still getting the desired results and
c) apply some common sense to the PTG readings before, during and after your test spot(s) to decide on the best way forward and
d) always tape up body lines and panel edges where there is an increased risk of striking through.