The NIST-developed Object-Oriented Finite Element code (OOF) is a is an open-source project for the segmentation, meshing, and finite-element analysis of microstructural images of materials, intended for a materials science audience. The OOF development team has recently completed expanding the scope of this tool to include history-dependent properties, motivated by crystal plasticity. Among the challenges faced are the complexity of a mature code base, the need to retain a high level of generality and ease of use while making these changes. The team's development approaches to these recent modifications and emerging goals will be described.