Dioptre is a measurement of inverse focal length, so +1 is 1m, +2 is 500mm, +3 is 333mm, etc. Therefore a dioptre used for close-focus work would want to be a very strong one (at least +5) for it to have a focal length short enough to be used as a lens in its own right. You can stack them though, with a +2 and a +3 being very nearly the same as a +5. I don't know enough optics to say how well that will work but my suspicion is that stacking them like that will lose any a(po)chromatic properties.

As for aperture and bokeh control, you can buy a set of cheap holepunches from the hardware store and stamp your own arbitrary patterns out of thin brass sheet. If you wanted to be ultra tricky, try to get a bit of glass that is clear in the centre and darker towards the edges to use as an apodisation filter and you could build your own STF clone of the Minolta classic. There is nothing with better bokeh.