I think you can can achieve your desired result without editing the files to make the CTP curves less dramatic. I would not take the path of doing an ‘extra image edit’. Well, there would be a lot of fighting before I did.
All about process control Mate, I agree with Jeff that G7 is probably going to be your best bet. The G7 profile, Gracol2006 is based on exactly the same press run data as ISO39L - using ‘non-standard’ variables with G7 methodology will get you absolutely knocking on the door of an ISO Coated V2/Fogra 39 proof. I have used dramatically non standard UV inks on a KBA 162 printing fashion posters and had a result that looked ‘exactly’ like the ISO Coated/Fogra 39 proof (except the proof was much, much smaller!).
Your situation sounds a lot like the flexo world - in which i also thrive . In Flexo you really need to make sure every possible variable is ‘in tolerance’. You may still be required to give the CTP curves a hefty shove to get what you want - but is it possible even using different hue inks on different substrates to get a fairly ‘close visual match’ to a Gracol2006/ISO Coated V2 proof (gamut permitting).
While your Minders say they can’t adjust ink/water, I don’t believe them! Roller nips, plate pressure, blanket pressure, ink tack etc. A lot of the answer lies in the press-room.
I’ll bet if you start documenting press variables as seen in the G7 PreQualification Kit it would change your situation for the better. It can take a while, but you can get there.