Well, I found spare 25K lin Pot and tried it... it works perfectly fine

The Squarewave gives this delay an even more interesting sound range...
I love it! And I'm gonna try the Sample&Hold Option you were talking about... I also wanted to add a second delay time pot and a DPDT, to easily switch between two preset delay times
So, now I need a new enclosure for this sweetie.

And while I'm experimenting with it anyway... is it possible to make the LFO switchable too? I mean turn it on and off?
In my imagination it would be easy to put a switch between R34 and Q3... but maybe my imagination simplifies things too much