I teach on a backstage theatre production diploma and have to train up 16 - 19yr olds on followspots as a matter of course, regardless of whether it’s required in our shows. I find that with a few exercises and just a few hours of practising they can often achieve a passable result. It’s important to remember that in a educational setting, you have to give students the opportunity to fail. If you prevent them from trying out new things because you’re too wrapped up in your (or the director’s) own production values, pretty soon there’ll be no one left in the industry. As for the safety aspect, again I train young people to work at height on ladders, access towers and indeed, operating a followspot from an open gallery with a 4m drop below them. As long as any structure you provide is constructed by a certified professional, adequate training and supervision is given to the students and the whole operation is risk assessed, I can’t see that any reasonable OSH officer would have cause to block it. In terms of the followspot itself, you could always look into hiring an LED one - smaller and lighter to carry up a tower/platform and very little heat kicked out in operation. Of course I’m not familiar with your venue, but even the cheap ones are capable of a comfortable 20m throw distance.