you can veg under hps but your plants will stretch more. Mh lights helps them to develop tighter nodes which lead to more budsites. As far as anything else you should be fine
I have been vegging under hps for a few weeks with a little bit of 5k cfl added in to add more blue to the spectrum. My plants were already a few weeks old and established when I started with the hps. It's been just fine. However, I just germinated 2 autoflower seeds and they were stretching too much for my liking. I moved the seedlings over to cfl's in a different cab that I have. They may have been fine, but with the cost of auto feminized seeds I didn't want to take any chances. I'll move them back after a few weeks.
They do make hps bulbs with more blue in them, but they are pricey. Probably cheaper to add in fluorescents. Here is the link to the better hps bulbs. http://www.eyehortilux.com/products/