I was thinking "add all the things that make packages insufficient to use as an infrastructure" :-)
One thing is autoconf support for those doing ffi. We might also want conditionals in package specs (cpp enough?).
I don't see Makefiles as part of a cross-compiler story. Rather, I see an enhanced package system that includes a subset of makefile functionality (e.g., Hugs' import chasing and GHC's --make functionality).
And the enhanced package system is implemented in each compiler? Or just once in the infrastructure, perhaps by a script? Or a mixture of the two? One difficulty is that if the infrastructure requires certain extensions to the package system, then we can't start using it until new compilers come out that have the required extensions. There are some aspects of the infrastructure that I really don't want to provide in GHC as part of its package system: the details of building libraries several ways, installing them in the right place, building and installing documentation, etc. etc. So I think this stuff belongs in the infrastructure one way or another. However, I'm not proposing to implement this stuff (I'm hoping someone else will volunteer ;-) so whoever does the job gets to choose the implementation strategy. Obviously we'll help out with any extensions to GHC that are needed. Cheers, Simon