Hi Aimee, as you have already received a lot of feedback from study sources, I'm going to share a little about my feelings as a consultant implementing the model and now as a client.
I think the first big point is to assess the maturity of your teams in relation to DevOps and also automation. Platform engineering tends to evolve companies' DevOps model and cover possible gaps that this model brings. If they are still in a more traditional and siled environment, perhaps the first step is to leverage the DevOps culture and then bring in platform engineering and practices and an IDP. Which brings me to the second point which is automation. How much of your infrastructure and services do you already deliver in an automated manner? Many companies already jump to an IDP without having the technical and tooling capacity to implement an end-to-end infrastructure in an automated and secure manner. With this, I strongly recommend that you evaluate automation maturity and the potential to improve this maturity. Because having an IDP to just generate a ticket for the infrastructure team to upload an environment, you will end up placing another obstacle in the process and overlapping an activity that any ITSM tool would already cover.
I hope I helped and good luck with the implementation