I have worked with aircraft with such tech problems. At a major airfield, the main holds are likely to be some distance away and require a climb to maybe 7-8,000 feet. My personal preference was to hold the aircraft on radar - simple racetrack close to the downwind leg which required only instructions to turn at either end. The crew could then deal with their problems and the aircraft would always be close enough to a quick approach when the crew was ready. Of course, a lot depends on local traffic and procedures so this may not work everywhere.