Creativity is something I like in a budget class. In fact I have always preferred keep in the dash board in place for appearance reasons. We had rules in place to require at least part of the stock dash to keep a more finished look. I gave up on that as so many stock dash boards were just old and falling a part anyway, but this FG replacement was made on the cheap at home and once finished should look really slick. I like it.
BTW... defroster. You maybe able to ditch the blower motor. I have run in rain races with no interior fogging issues. I have my stock early heater box with the vents fixed to defrost mode. I still have the blower motor, but it has not worked in years. It seems just driving moves enoigh air due to high presure at the base of the windshield. So you may get enough air flow and may not need the blower motor weight.
Just a thought - depends on where you live. Here on the east coast it's worth having some kind of defog. Not often, but at least once or twice a year we have races where the guys without drive around trying to reach the windshield with a rag!