There is a variety of research on intelligent virtual assistants (IVAs) and omnichannel, which is subject-specific. However, since people need assistance on multiple topics from their preferred channel at any time, it is crucial to integrate these concepts efficiently to provide a better user experience. This article proposes to build an omnichannel IVA that assists the user on multiple topics according to the environment through different digital channels, in various interaction formats such as chat, voice, and immersive, with software architecture that easily integrates different components of the IVA ecosystem. Its main contribution is to serve as a guide for architects and software developers who need to implement an IVA with flexible omnichannel middleware architecture, facilitating the integration of technologies, channels, and services, seeking to provide a unified service to its users.