Sounds like your on the right path, couple recommendations I would make
1. Go bare bottom and higher flow, makes it easy to remove any detritus and should keep it suspended so the filter can pull it out.
2. Use egg rate and make your frag rack yourself, you may want to adjust the height and that's easier if you make your own rack.
3. A 6 line wrasse makes the perfect frag tank fish IMO
, they'll eat most pests that could become an issue.
Other than that I think you've got the right idea, really not that hard.