Hi @AvochAndy, thanks for the sharing. Your pointers made me realise that there could be other methods other than GCP (which is resource/expense intensive and time intensive with regard to the necessary strategic GCP markings), in this case, the mentioned QGIS. This made me look into the accuracy of QGIS vs the traditional GPS and how accurate it could be...which then brought me to another topic of figuring out the accuracy of RTK/PPK drones vs the added input of using GCP (see link of Pix4D: https://pix4d.com/rtk-ppk-drones-gcp-comparison/).
In agreement with @Dave... At first thought, local accuracy should be good enough (X and Y coord should be good and relative accurate too) but I understand that the Z-coordinate could be hugely affected without a proper and accurate GPS marking or GCP. Well... depth of vehicle damage and indentations and relative height and position of the damage areas on the body of the vehicles are important. The depth of damage, scratches and gouge marks on the roads would be important too (Z axis again)...hence my reservations now about doing away with GCP. I'll still try to find out more if such measurements could be accurately taken without GCP...but I'm all ears to further advices.
Well, like I said...being a noob, it leaves me to researching for more and I do hope that I'm on the right track to getting an indication of what drone, positioning accuracy hardware/software and photogrammetry programs to acquire.
Once again, thanks so much for all your help. I'll be listening in for more . Have agreat weekend. Cheers!