I'm thinking the syntax would be something like AlternativePrelude="MyPrelude".
There is a general principle that the semantics of a program should be completely described by the source code itself, and not dependent on options that may or may not be specified elsewhere. Hence, the idea of adding {-# LANGUAGE #-} pragmas, so that the source code is self- contained. Specifying {-# LANGUAGE NoImplicitPrelude #-} together with "import MyPrelude" satisfies this principle, as does {-# LANGUAGE AlternativePrelude="MyPrelude" #-} in all files where it matters. But the difference in usability is slight. If you are suggesting that {-# LANGUAGE AlternativePrelude="MyPrelude" #-} should somehow escape the scope of the module it appears in, then I think we heading for less firm ground. Regards, Malcolm