Many issues involved here. A flat floor theatre could possibly be done with those heights but the final result is not acceptable if you have any sort of competition within 50 miles(or the prospect of competition coming into your area).
Are you at liberty to rip up the concrete and dig down? That would gain you screen height and allow full stadium seating.
Are the columns evenly spaced thru-out? What is the average distance between?
If your area does not have a theatre, you can make this work. I'll suggest a good architect who could help- Paradigm Design in Grand Rapids, MI. Bill Brunner is working on my project.