Not sure if this topic is active. Here is some feedback.
1. Decouple the datatypes library from other core SystemC libraries. In other words it should be a light stand-alone library of its own.
2. Single unified bit vector library for all widths (like ac_int<W>). However having the range function for behavioral modeling (not synthesis) is also very useful. Currently we use the following c++-11 feature:
/*----------------------------------------------------------------*/
// This uses a neat template alias trick introduced in C++-11
// to hide the underlying type of either a