You originally asked 2 questions:
1. Should I change my vegging plants from MH to HPS to try to induce minor sexing?
Do not change your bulb to HPS while vegging your plants. The whole benefit of the the blue-tilted light spectrum of metal halide is that it decreases stretching as compared to HPS or any other time of lighting. The blue-tilted light spectrum benefits early alkaloid production. Furthermore, it is the light cycle and not the bulb spectrum which triggers flowering.
2. Can I flower them, determine sex, and revegetate the plants?
Yes you can! You can revegetate flowering plants all the way up to harvest. You simply put the plant back in an 18/6 to 24/0 cycle.
**Note: If revegetating the remainder of a harvested plant, be sure to leave several small growth buds. Also, fertilize with a high Nitrogen solution. However, be very careful not to drown the plant. It has the same root system but much less foliage -- don't overload it.
Good luck with your grow.