It would be very useful to have a document class that contained a union of all known environments, so that in the early stages of writing a paper, before you know exactly where you are going to submit it, you could write it in the "Uber Document Class" and use environments as needed. Then when you needed to actually submit the rendered PDF, you could change the document class to a specific one and the environments would be mapped to existing environments in that corresponding class and if they didn't exist, then a predefined mapping for the target class defined how to emulate the environment.
For example, some classes contain some subset of special environments for addresses, phone numbers, email addresses, proofs, lemmas, theorems, corollaries, etc, and since there is no, as far as I know, class that contains all of them, you are forced to guess your best match and then later do allot of manual changes to properly use the final target document class. An Uber Document Class might seem like overkill, but for the very early stages of writing, I think it would be very useful, and in the long run it would improve productivity of writing.
