I am another to use my drysuit for buoyancy control and soon it will seem easy, although after a few months diving here in Los Angeles when we go to the South Pacific it is fun to watch my wife lift her left shoulder to dump her wetsuit. For me at least, even with heavy fins, ankle weights are a complete necessity.
Keep the drysuit for the future. The more important lesson I think is that if it is your thesis advisor you must realize that she pretty much controls your future. If the work is for hire and is paid for by a company, then what I would do to get some reimbursement and not piss off my advisor is to buy the suit then rent it to myself and have the company (not the university) pay the going rental fee each time I dove.