Hot mud dries so hard that it's a pain to sand, so I usually only do the first layer with hot mud and mesh tape, then use regular weight standard mud for the 2nd and 3rd layers. And as suggested below, thin coats are key.

Acrylic would probably be too brittle. I'd look at rotomolding that one, which is likely how the one in the picture is made. But it you want to thermoform sheets, you could try that, but use nylon, ABS or something like that.

I got tired of messing with the wire nuts, so I just use push-in connectors now.

Sean Penn.

except that you can shock yourself on a turned off fixture since it's always hot.

The issue with the spool diameter increasing as you wind string on it is a differential equation, I did something similar in my Dif Eq. class for the width of cassette tape reel. But I'd just use multiple wraps on a pretensioner pulley.