I don’t know, if this applies for ALL hosts, but afaik you don’t. It’s because the output of your plugin changes the input of subsequent plugins.
In ProTools it works this way: you get your plugin for selection only if the input bus layout matches (either number of channels or channel layout). Your plugin can require a certain layout in the preferredBusLayout, see the ultimate JUCE 4.1 MultiBus Guide from fabian. In that case for example a plugin for a 5.1 layout will not show up in a 6.0 bus.
You get not only one plugin to select but one entry for each possible output layout.
You have to be aware, that selecting a plugin variant with different input and output channel layouts, that all subsequent plugins will be changed to match the new layout (and pro tools gives you a warning, that it will alter these).
If a subsequent plugin doesn’t provide a variant with the new input layout, it will be removed.
It would be interesting how other hosts behave with changes of the bus layout dynamically, one for the Collaborate knowledge base…