I think it could be even deeper down, because not everybody develops using BIDS or Visual Studio or the UI. If I run an Enterprise-only statement in a query window, I should be able to see an attention event, or something similar to the deprecation warning, when using features that don't run on the target you've specified. When I know I am targeting standard or lower, I can simply check for that event. Much simpler than reviewing all of the features and code against some checklist. This could be set at the database level and/or server level, so that you can be working on multiple dev databases at the same time, potentially with one targeting express and one targeting standard... then an event would be raised if, for example, you used CREATE PARTITION SCHEME. But you'd also want to catch server-level things (e.g. BACKUP DATABASE ... WITH COMPRESSION).

I think this is important, yes, but I'm unsure how well such a feature could be implemented in disconnected tools such as SSIS. Given that the dev teams work almost independently, I'm not sure how the SSIS team could know and keep track of which SQL Server features belong to which edition. Nevermind the ability for users to use custom SQL in something like an Execute SQL Task that SSIS surely couldn't validate at design time.