The CDISC Reference Model is not a mandatory standard so you can adapt it to suit your needs. However, most of this community would likely advise against. The model has been developed by hundreds of practitioners to reflect best practice and inspector expectations. If you make changes, you’ll likely be out of line with what the rest of industry is doing. Inspectors might struggle to find things. Other partners (eg CROs) will have similar problems. I’d advise keeping as close to the model as possible.