Multiple template sources

Current template system works for simple cases. With anything more complex and involving data from not directly related entities I feel forced to create custom "bag of values" entities, just for the purpose of sending an email or generating a document. There's also no easy way to add arbitrary variables to templates. I mean variables that are not connected with any entities, something like for example current date. I think it would help a lot if you could set up multiple "macro sources" and add arbitrary parameters too (just like you can create parameters for a business process).