Has anyone here ever modded a vert to have stock style rear defrost?

I found most of what I need. So far I got a heater panel with stock AC and rear defrost controls.

I got a complete wiring harness from dash to glass from an ebay seller. I got a NOS rear defrost switch from ebay.

Two things Im wondering about;

first, should I replace my verts rear glass with heated glass or just ad an aftermarket heater grid on mine with a Frost Fighter setup? The interior shop that did my convertible top 2 summers ago told me $690 to replace the glass with the surrounding vinyl section. Pretty steep and not at all worth it. But then again AutoMat in Hicksville NY has always been crazy expensive. I will check one other shop then I will make a decision. Anybody have opinions on this? I did Frost Fighter 30 years ago in a 67 Camaro and I was really happy with it.

Second, I had my mechanic print out the wiring diagram from AllData for the Defogger Circuit for an 85 LX. According to the schematic the white/purple wire gets key on 12 volts, the yellow wire goes to the starter relay and the diagram says Hot At All Times.

I'm no electrical expert but isn't that gonna blast the defrost switch and circuit every time I start the car?