Modernization of computational models is crucial for accelerating discoveries and enhancing our understanding of Earth system models. In this context, the EAGLES (Enabling Aerosol-cloud Interactions at Global Convection-Permitting Scales) team is actively engaged in developing an exascale version of the 4-mode Modal Aerosol Model, known as MAM4xx. To facilitate its integration into the host model EAMxx, MAM4xx is designed as a column model. This design allows us to devise unit tests and standalone testing of individual components. MAM4xx is a flexible, modern software tool that can be employed both as a column model and as a component of EAMxx, thanks to its complete redesign. The new design enables scientists to test new approaches in a standalone model before deploying them in EAMxx. Finally, by structuring MAM4xx around units of "aerosol processes," we pave the way for future enhancements to the microphysical components and algorithms of MAM4xx. The team leverages cutting-edge software tools for developing MAM4xx to ensure maintainability and ease of use. Specifically, MAM4xx employs modern software like CMake, C++ (with Kokkos performance portable library), unit testing, validation testing, code coverage analysis, and GitHub Actions to ensure high-quality software development. This initiative aims to significantly improve aerosol prediction capabilities in the EAMxx (E3SMv4 atmosphere model) and is pivotal for understanding a variety of atmospheric phenomena.