as with most things... what is appropriate for one person, another will say is unacceptably simplified
the principle in EigenD is to allow 8 slots, which a user can populate with the ones they use most.... 8 presumably chosen as its convenient for the pico (and also splits on the tau/alpha), but its easy enough to extend this to N.
your approach, no this not possible as there is no way to build scales... (and more generally the 'arrays' it uses), it would not be that difficult to write an agent to do it however, and could be more 'generic', e.g. allowing you to pick notes from any arbitrary scale (e.g. your example is allowing sub selection from a chromatic scale, but it could be from any scale)
but to be honest, I use chromatic all the time anyway, so its not something ive got time/interest in building... and I'm also not convinced its more useful than the current 'slot' approach.
... like most things with software, because there are so many things you could change/improve, you have to 'pick your battles ' :)
one thing you could do, if your struggling with the browser, is to create your own talker, with lots of actions like
keygroup 1 hey scale to major set
keygroup 1 hey scale to minor set
keygroup 1 hey scale to chromatic set
keygroup 1 hey scale to [0,1,2,4,5,6,7,8,9,10,11,12] set
etc.
this talker could then be activated from eigenharp or stage as you wish
if you dealing with a relatively small number (<20) of scales id say this would be pretty acceptable.
(also it become less workable if your on a tau/alpha and want lots of split variations)