Thanks. I must have used wrong keywords for the search, because I have definitely seen your MDF adapter before.
My idea is similar but the intention is to fix it like the second system. So that the adapter stays near the material surface all the time.
I did experiment with acrylic and milled several layers which glued together and it seem the idea is workable. In this way I will have a transparent top.
The other problem is that if the tools goes near the edges, the adapter will hit eventually a holding bracket.
Either I have to change the way I fix the material or what comes to my mind (and have seen on a YouTube video) is to make a dense brush, about 3 cm high which will fence the tool area but deform if a bracket is touched.
Tomorrow I plan to start learning the brush maker's trade.
I've bought a large wall painting brush and intend to drill a line of holes on the lower side of the adapter and glue bristle flocks into them, just like the normal brush.