Candles as such are actually no problem. It's dripping and smoking and placement that cause the damage.
If they're in containers, and the wick is kept trimmed and they're not near the walls then they're harmless.
Decent gel candles burn for days and hardly need trimming at all so never smoke.
I suspect a lot of people who light candles do so because they need light, not purely as an act of reverence. If there was a bit of a bench in there, they'd put their candles on that, rather than on the wall.
That, plus notices, could be easily tested before the ultimate solution is used.
