Thermostatic shower valve with tankless gas heaters
Other than scald prevention, which isn't much of a concern with 48°C water, the other "features" are being able to set a maximum temperature, and attempting to maintain temperature when the pressure on one side dips.

Since you say that you set the heater near your bathing temperature, then it sounds like those other features won't do much for you since you're using almost 100% hot water rather than a mixture of hot and cold.

I don't set my water heater much higher than yours, but I still like the ability to adjust the maximum temperature in my kids bathroom.  I have it set where it doesn't even get hot enough for me to take a good shower, but its perfect for their bath and can't get hotter than they would like.