Safety tap

My wife has dementia. She likes taking baths. One day she nearly scalded herself by emptying the bath while still in it, replacing the plug and turning the hot water tap fully on. She then panicked and neither turned off the water, nor got herself out of the bath.
For the next few days I agonised over what to do. I investigated thermostatically controlled taps but the cost of all the required parts was estimated at approx $2,000 with installation on top.
In the end I thought of dis-assembling the taps, that is removing the handle assembly and making a replacement handle that could be placed on the tap stub, the tap operated, and the replacement handle removed and stored away from the bathroom. This works well BUT is dependent on remembering to remove the handle once the bath has been filled. I've put up a couple of reminder notices.
I designed and made this some time ago but didn't bother to post it because I though it too specialised. This design will suit only a small range of