A thought, primarily as a note to myself for further investigation: the current OS X framework build support and, to a lesser extent, universal build support have added a fair amount of special-case cruft to the build process, primarily in configure.ac and the main Makefile.  Over the years, the build tools have evolved and gotten smarter (and more general) about SDK support and arch support using xcrun, as they were generalized to support iOS vs OS X builds.  But, if it is necessary to do separate compile/link steps to support iOS framework builds because of the multiple SDKs, it *might* make sense to integrate those into the main Makefile and to isolate the framework build steps (for both OS X and iOS) to be more of an add-on step.  The potential positive impact might be to simplify the current main Makefile and configure.ac by centralizing much of the framework build specific steps scattered throughout the Makefile *and* it could also simplify and speed up the iOS builds by not duplicating the platform-independent build steps.  It might even be a useful abstraction for other non-Apple multiple-arch or cross-compilation builds.

Another factor to consider is support for building third-party extension modules standalone as opposed to building as part of the interpreter itself.  It would be nice to be able to just use the traditional Distutils-based process for third-party extension modules.  For OS X universal builds, we get that essentially for free because of the tool chain support for multiple archs.  To do it automatically across multiple SDKs would require adding smarts to Distutils to do multiple compile/links and lipo merges.