As increasingly complex missions to the Moon continue to be planned for the upcoming years, several key infrastructure requirements are needed to ensure mission success. Position, Navigation, and Timing (PNT) services are one such technology, and recently the use of terrestrial GNSS signals has been successfully demonstrated on the lunar surface. However, there remains international cooperation towards the development of new GNSS-like infrastructure specifically targeting lunar missions, to provide an accurate, redundant service. While several different approaches to establishing a reliable communication and PNT network are being explored, one approach focuses on the use of additional navigation signal sources near several of the Earth-Moon Lagrange points to enhance the GNSS signals provided by terrestrial networks. Such signals can be used to improve positioning performance by up to two orders of magnitude compared to terrestrial GNSS networks alone, while remaining fully independent and operational as a standalone PNT solution for use on cislunar missions. This paper discusses the mission design of a lunar PNT network consisting of several spacecraft around the Earth-Moon L2, L4, and L5 points, located in specific orbits to target the key areas in which these services are to be required while remaining stable relative to the Earth-Moon system. Furthermore, this paper will discuss methods of transfer from low-Earth orbit into the relevant operational orbits, and the feasibility of establishing such a network.