With a conversion ballast you will be harvesting half as often than as in a sog or scrog set up, which is fine, but it's also less weed. If you aren't going to sog or scrog then all you would need is a combo mother/clone area and a separate grow area. Take a clone from your mother plant, put it in your system, when it's time to bloom, switch your ballast from MH to HPS. 2 or 3 weeks before harvest get some cuttings from your mother and start them in the cloner so that they will be ready to go into your system as soon as harvest clean up is done. Keep in mind your HPS will be on 12 hours per day and mothers and clones will have 18 per day, and they can't interfere with each others' light schedule.