re: 2-shot they have to be converted to path regardless, so do that first, then one can attempt to thicken the lines and up the spacing.
it's necessarily going to look a lot fatter when done as a doubleshot, basically.
re: dyesub. the first color scheme should be ok for dyesub. black on tan should come out with some nice contrast. the second design won't dyesub at all, as the print must be darker than the keycap. basically the text will have to be black to get that out of dyesubbing.
re: 2-shotting very thin lines or inadequate separation. it will almost certainly just look bad, and it will be impossible to do QA. don't bother. think about what's happening. the first shot is formed by injection molding with a grid pattern behind it. then, a second shot of plastic is formed around the first shot. the grid pattern draws the second shot plastic through the first shot. however, both pieces of material are basically molten at this point, and very likely the only thing that keeps the legend formed is the engineering constraints of the legend design. hence, breaking these constraints will cause the legend to melt into the second shot. this will only cause the "clean" bit of discoloration you are imagining if the mixing forces are isometric and normal. if they're not, they could end up mixing in highly unpredictable ways and you'll just get weird ugly tie-dye keys.
