My first attempts at avoiding recursion were directed at performance enhancement and not at expanding the functionality of the core. Cameron Laird kindly pointed me to Christian Tismer's Stackless Python and thus opened up new horizons in my mind.
I have read the material at Stackless Python , but I did not look at the code - understanding Tcl's core is quite enough of a challenge for a novice programmer, without adding Python to the menu. I am quite positive that those readings influenced my thoughts very deeply, but it would be hard for me to pinpoint the exact influence. I definitely first thought of using my flow managers as safety barriers in the C-stack while trying (and failing) to understand Christian's multiple dispatchers - and I'm still not sure if they provide similar functionality ...
I finally got the energy I needed to transform vague ideas into concrete code thanks to Andreas Kupries' encouragement.