A. Jordan Nafa

Thanks for opening this @mjskay! The current ensemble implementation [for models of class `brmsfit` in `{marginaleffects}`](https://github.com/vincentarelbundock/marginaleffects/blob/main/R/methods_brms.R) is built on top of [`brms::pp_average`](https://github.com/paul-buerkner/brms/blob/master/R/model_weights.R) since it relies on expectations for stacked/model averaged...

In theory, manual specification in the model block via the `stanvars` argument would work, but only in the case of very straightforward models. Consider the case of a multivariate outcome...