The Netherlands currently lacks a large scale aggregation system which can unlock decentralised flexibility to improve the reliability of the electricity grid in the presence of a significant amount of variable renewable energy sources. In this reserach, the aggregator blockchain technology is perceived as an enabler for a decentralised flexibility model. It is however uncertain how the implementation of both systems fit technically and institutionally in the environment of the Dutch electricity sector. This paper analyses implications of the aggregator and blockchain technology in unlocking decentralised flexibility by considering a system integration approach. Using the comprehensive design framework, a conceptualisation of system integration in energy infrastructures, many challenges regarding the aggregator and blockchain as flexibility model have been identified. Both systems have shown to have major implications that need to be overcome to ensure successful system integration.