Ok.. I'm not sure I totally follow.
Whe you pick 01 - "insp. specifications from QM" in the COA profile being used, the specs shown should not come from the inspection plans.
According to the info on the FM (and my knowledge of it), the spes should be looked for first in the inspection lot it self. These are usually stored in table QAMV. Once the specs are copied to that table, (when the inspection lot is released), they can't usually be changed except in rare cases. Changing or deleting an inspection plan is not one of them. Only if the lot is in a state where the sample can reset and the specifications reread from the plan.
If it can't find inspection lot info, it takes the specs from the MIC. It doesn't say what it does if no MIC is found so I guess you could have create all your characteristics in plans and not used any MIC's. That's not a good idea and not a good design so I'm hoping that's not the case! Let us know if it is.
Below is a screen shot of the config for the 01 - insp. specifications from QM. I also included the help screen from the FM. Can you verify that your 01 selecion is using the same FM as shown below and provided by SAP?
What you'll need to do is configure a new choice for the origin of specifications, say a Z1 - "specs from current plan". You'll then need to have your developers take the above function module, copy it to a new "Z" function module, delete all the logic about getting the specs from the inspection lot and instead put in all the logic needed to find the right inspection plan, get the specifications and return the correct value to the SAP script. You shouldn't need to change the SAP script. Just the FM that retrieves the specs for you.
Craig