One of the crucial issues facing enterprise modelling (EM) practices is that EM is considered technical, and rarely or never has a social focus. Social aspects referred to here are the soft aspects of the organisation that lead to organic organisation development (communication, collaboration, culture, skills and personal goals). There are many EM approaches and enterprise architecture frameworks were proposed recently. These cover different enterprise aspects, perspectives, artefacts and models with different qualities and levels of details. Yet, the imperative determination has overlaid the declarative exploration in EM as a necessity of the design effort. Rethinking the assumptions underlying EM should bring a new and different understanding on how EM can be tackled within the enterprise, in particular the joint development and optimisation of socio-technical systems. This paper discusses EM from a socio-technical systems (STS) perspective, and towards forming a new model of EM that is driven from STS theory and combined with STS practices. Then proposes a conceptual integrated model that incorporates the new concepts of STS toward building an EM framework for balanced socio-technical joint development and optimisation. The approach is illustrated in a scenario from healthcare industry. A combination between modelling and STS practices proved powerful for holistic IT modernisation, future work discussed toward the end of the paper.