I'm working on my own SliTaz version that I'm building with the help of buildroot. I'm planning to do the following (so far, more updates to come):
1. Compile it against eglibc to maintain binary compatibility with the SliTaz packages while reducing build sizes.
2. Use the latest Linux kernel it supports with as many functionality enabled as possible. This will also include the building of several modules into it like dialup, wifi and bluetooth.
3. Use Xorg with the majority of drivers include for input and video.
4. Use Busybox for the majority of command line utils.
5. Use Busybox's init and mdev instead of systemd and udev.
6. Drop SpaceFM in favour of something else, possibly ROX-Filer.
7. It will include the latest (working) copies of the SliTaz scripts and programs (like Tazpanel) with possible modifications by Aleksej.
It's still a work in progress so any suggestions will be helpful.
EDIT: Added the bit about Xorg