1. My suggestion
No, not exactly
My idea is to multiply the existing selection shapes (cube, sphere). I'll explain better:
Structure:
Cube Op (Tesselated like 8x8x8)
Select (selects some faces of the cube with a cube or sphere)
'Multiply Select Shape' - (an option in Select Op or a new Op) - this operation implies multiplication of select shape (cube or aphere) over the Cube
in order to achieve pattern selection (like 2 faces selected then 2 faces unselected and so on). Is it any clearer now?
As for the 'select by texture' trick, it falls out of control quickly because UVs are involved (which have always been tricky). Besides, I have not managed to make it select just one face at a time (I suspect it is based on vertex selection). Anyway, I'll try to learn better how to use it.
2. Your idea
I'm all for Grow/Shrink selection option or op. It has huge potential!
Storing selection under some index number seems OK (just like old times, uh?), but imho WZ3 had a bit better selection system in terms of productivity (tabs vs numbers).
Yeah, and maybe Store/Load Selection ops may come in more handy for compartibility. But it'll require to populate 2 more ops (in case you separate Store and Load selection in 2 differnet ops) across the structure...
So, you are the code guru, and the choice is all yours.