Being the designer of the system - with Pierre @Pandagrapher for the GUI, and the participation of the whole team including Ingo @heckflosse to optimize the code and improve functionnalities - , there is no “one” right solution. But the best one is the one you master.
Both systems work with their advantages (and disadvantages)…
The advantage of creating a second Spot…is that there is another one and in particular to be able to play on the differences of positonnement and thus of the references (hue, chroma, luma).
Some duplications are obviously necessary like “excluding spots” (which also allows you to do the “inverse” functions) or “merge file” in “Color and Light” with “Multiply, Soft Light, Overlay, etc.”
If you use the most complex functions, like for example “denoise”, “wavelet”, “retinex” you will probably want to use a spot - a tool.
Another tool can (almost) work alone in most cases, it is “Log encoding” associated with Ciecam
Working with a spot and several tools has the advantage of using the notion of object…and makes it easier to read the image…and modify.
So in summary the system allows what you want, it has its limits, for example the masks do not all have the same functionality, graduated filter are different, the GUI is already complex, but works well, and can certainly be improved, etc.
Of course we can still make improvements, but it seems to me that it is necessary to take a break in the development of new features