I think the lack of demand for it has been an indicator that ranges with additions are just enough. We're currently looking at adding optional primitives to ranges in a Design by Introspection manner to support bulk streaming of data.
How about adding a byte buffer concept alongside with ranges? I'm thinking an API similar to Netty's ByteBuf but using D's compile-time capabilities instead. These would be valid ranges as well but offer direct byte access on top.
It would be great if the reflection info could be outputted to a separate file for those cases where its only needed during program initialization or used by external tools.