Well I found this to be a convenient, unorthodox solution.
The kernel (RT_PREEMPT 4.20.0 on BeagleBone Black) and the image derivates from piCore with some needed customizations.
While I understand it´s not what the tce-update script is intended for, it worked enough for me. I´d rather have a proper config file for the tinycore version, (like for example source.list for debian) but unfortunately Tinycore
has its bits scattered everywhere (like within / and /usr/local),
or even sometimes has dupes (like kernel modules)
there is no consistency between the packages / platforms / version (like for example dropbear is present into armv7 until v7.x included, but disappears from v8.x
and worst of all, there is a mess of documentation (confused, outdated, in different places)
and no proper tools for remastering, it took me a while to figure out what config options exactly were needed to configure a kernel to load a tinycore image.
That said I like the simplicity, modularity of Tinycore as well as the philosophy running the whole system from RAM as well as the flexibility of the extensions. This allows me to make a bare system for a given platform, and to quickly morph it into whatever I want. Without going all the way from compiling everything into an image like yocto + angström linux