This paper proposes a 5G network data space targeting the collection, storing, and sharing of metrics generated by 5G infrastructure, such as latency, throughput, and network slice performance, for universal access by applications. The primary challenge is standardizing these metrics across commercial vendors (e.g., Nokia, Ericsson, Huawei, Samsung) and open-source implementations to ensure interoperability in a decentralized ecosystem. Current approaches, such as NWDAF, O-RAN, and Gaia-X, face this interoperability challenge but remain limited in scope. We present a vendor-agnostic framework that supports multiple metric-gathering methods, including standardized mechanisms, and proprietary telemetry protocols, to enable cooperative data collection The paper includes a detailed architecture which is organized into four layers—Data Collection, Standardization, Data Management, and Application Interface, providing solutions to vendor heterogeneity, fostering scalable, secure, and interoperable data sharing for advanced applications and services. This work is a conceptual and architectural foundation, that outlines the main directions for such a future 5G Dataspace, with validation and prototyping left to subsequent research.