To fully control the temperature you might have to also add cooling capabilities, because the fermentor will be enclosed. The must generally only needs warming until fermentation starts. After that, it generates its own heat.
I use the brewbelt to get the temperature to a good starting place for the type of wine, then remove it after fermentation starts. Many times after fermentation slows, because my fermentation room is cold, I add the brew belt again, only if I need higher temperatures for the type of wine I am making.
I have a friend in Canada whose fermentation room is very cold. He places his fermentor inside a large tub of water. He buys the longest fish aquarium heaters he can find. He places two of the heaters in the water of the tub. Since the heaters are adjustable, they will shutoff when fermentation generates its own heat; then come back on when fermentation slows.
A blanket can be placed around the tub and fermentor to hold in the heat.