deb2tcz is meant for simple packages and was made in a different day when there were far less extensions already built and available. In fact, the first solid working gtk2 I used on Tinycore was that from Debian Etch, before we had polished our own. But today, deb2tcz is basically a relic.
Now, there is very little that is not available in the repo, and for what is not there is a good foundation for building. While I often if not usually use Arch or Gentoo's build scripts as a guide when building a package, portage or Arch's abs build system does not plug into Tinycore.
Though there is one use for the deb2tcz script, and that is for commercial stuff that often only comes in RPM or DEB format, so it is not totally historical or deprecated.