The contact dynamics is a complex problem which brings many difficulties when it comes to simulation. A particular way to express the contact problem has been developed by Moreau and Jean. The LMGC90 software aims at performing computation using this formalism. Being initially written in Fortran, the software suffers some limitations due to the language. Furthermore its architecture allowed robustness but the scientific requirements are becoming so demanding that this structure reaches its limit. Here is presented an original architecture were the software is split in several parts, each referring to an operator or a service needed by the formulation of the physical problem. This architecture is made possible by using some programming features as Fortran modules, or a fake inheritance mechanism. The bulk and contact modelling part are separated as much as possible and each part generates algebraic systems and interactions in an anonymous way to feed the contact solver. The storing of data is also put apart from the other modules so that all data relevant to the computation of a body are gathered at only one place. This structure makes extensions easier to add and still allows to have complex strategies management. The current software already covers a wide range of application fields like granular material, masonry structures, fracture of heterogenous media and multi-physics couplings. The design work presented here would aims at rend the code more flexible and simplify the couplings with other software or libraries. The ultimate goal being to be able to have a dynamic model representation switch at run-time simulation.