In this paper we propose an approach to optimization of reflection which combines flexibility and efficiency while implementing metaobject-based systems. The main idea is to flatten nested metainterpreter layers using a particular kind of mediator objects, which provide object/metaobject connection. One of the most significant features of the approach is that it allows to carry out what we called metaupgrading of existing software systems in a systematic way, efficient and transparent for the application. The meta-upgrading approach based on Interface Object technology can be efficiently used for system integration and re-use of legacy software components.