Perfect Orange Squash Maker

I like to drink hot orange squash. It's nice to put in enough orange, hot water and cold water to end up with something at a drinkable temperature. In fact, there's a perfect temperature for this drink, and if I wasn't ham-fisted I'd be able to make it at that temperature every time. This idea essentially fixes the volume of the drink in exchange for control over the temperature.

What I'm proposing is that the inside of the cup be marked with a scale starting at 100C at the bottom of the cup, and decreasing in 10 degree steps up the side. For a drink at a given temperature, fill with orange juice and cold water to the mark for the required temperature, and then fill with boiling water to a bold line marked near the rim.

It wouldn't be completely accurate, as the temperature of cold water varies from house to house and from season to season. It'd be a useful guide though as it would allow repeatability. People would come to know the temperature they liked their hot drinks at.

There would be room for several scales around the inside of the cup, corresponding to "just-boiled", "boiled 5 minutes ago" and "boiled 15 minutes ago".

Scales running from say 25C up to 100C would also be useful for drinks in which the hot water has to be added first - tea, for example. Again, it would probably only have a best accuracy of 5 degrees C.

At risk of making this idea too long, for the purposes of making squash there could be a separate scale on the cup, corresponding to varying strengths of drink from "10% concentrate" to "100% concentrate".