Probably OT, but in responding to this Q it occurred to me that a nice feature would be to be able to declare values for the offset/multiplier that are themselves either parameters or transformed parameters. I know nothing about how Stan compiles things, but the parameters-as-values case seems like it would simply require the user define things in the right order in the parameter block. The TPs-as-values case would require more look-ahead that might be a headache?