discussed privately with @ktf and @rbx. * It is currently [implemented on top in O2](https://github.com/AliceO2Group/AliceO2/blob/dev/Framework/Core/include/Framework/FairMQDeviceProxy.h) * Providing such an API directly in `fair::mq::Device` could save some indirections * Should the index-based access even replace string based channel facades eventually?