At the moment we don’t have a way to do this, mainly because we assume that observations are passed as arguments. Transformations itself should not be an issue if we would be able to track that f depends on l and s. At the moment we don’t have a handle on this but it could be added to the compiler.
Could you open an issue if you feel that this would be an useful feature?
– EDIT –
Thanks for trying to implement your model in Turing! 