Custom IPAM Design for AWS VPC (Not a traditional IPAM, read description and quote)

this is not a traditional IPAM solution request. The ask here is to design a solution to assign AWS VPC CIDR blocs using native AWS services- dynamodb, Lambdas, Service Catalog, CF etc Unlike native IPAM solution (where we track ip addresses of hosts or subnets), here we only track VPC CIDR ranges in dynamodb. This IPAM solution is to pre-populate Dynamodb with CIRDs (example /21, /24) and assign/un-assign as needed. When user requests vpc from Service Catalog, we verify there is an available range for requested CIDR and provision VPC and mark CIDR as in USE in dynamodb. Upon request to remove VPC, mark CIDR as AVAILABLE in dynamodb. Need someone expert in AWS and understanding IPAM need. This project is only* a request for design, will create a new project for actual setup or poc using above services and python. The steps I provided above just gives an outline. Expecting your proposed design to be robust with your expert ideas. As this is just a design, I'm considering it a small project.