There is no lsmeans package that I know of and it is highly unlikely that I will ever write one, but someone else may.
As for residuals, like many other properties of mixed-effects models, you need to be careful how you define them. You need to decide if the random effects are included in the fitted values or not. Perhaps it is better to define a fitted method for LinearMixedModel, which can then be the basis of a residuals method.
Could you open an issue in the MixedModels repository? It is probably better to have this discussion there.
The reason that I say it is unlikely I will write any lsmeans code is because lsmeans are a bizarre SAS construction from the days when we stored data on magnetic tape and programs on punched card decks. It would take so long to get a single model fit that users wanted every possible inference or diagnostic value calculated from the model, whether or not they made sense.