Installing a Harmon Accentra 52i TC into a 1950s brick wood burning fireplace with metal fire box

[wewantedcharacter]

Hello All!

Lurker, first time poster.

I recently bought a 1950s home that has a wood burning brick fireplace that utilizes a metal fire box.
The fire place has a fan system built into thew four corners.
I believe the theory of the fan system is to pull cold air using fans located in the bottom vents up around the hot metal firebox warming the air and blowing warm air out the top vents.
These bottom fans are powered by a 3 wire wire that is controlled by a switch adjacent to the fireplace mantel.
This whole circuit ties back to the a ground fault/arc fault circuit breaker.

I am looking at having a Harmon Accentra 52i TC inserted into the fireplace.
To avoid running the power cord where it is visible, I was thinking of cutting a hole big enough that a 3 prong power plug end can fit through through the metal firebox.
I would then install a rubber grommet inside the fire box hole.
I would route the power wire through the grommeted hole.

Next, I would disconnect the wires to the fan and install a metal temperature resistant plug gang box loosely within the masonry fan box.
I would then stuff the passage ways of the fan system with rock wool insulation and spray paint it black to trick the eye.
I could then plug the insert into a tripplite 1 outlet surge protector that is plugged into the metal gang and have the ability to disconnect the unit via the switch that previously powered the fan.

The fire box has a trapezoidal damper that would be locked in the open position.
After running 10 foot long piece of 4" ultra pro 316 Ti alloy single wall non insulated flex pipe from the unit into the chimney's existing 8" stainless flue, I'd stuff the damper area with rock wool insulation and install a damper block off plate to seal it off while also acting to support insulation.
The chimney is lined to the top and is capped with a stainless cap.

Because the house is from the 50's and drafty as is, I do not think id need to utilize an outside air kit.

I was told by an authorized harmon installer that I do not need to pull a permit.
Is this true?

Do I need to reach out to my home owners insurance company?
It seems that a pellet stove insert is much safer than a wood burning fireplace...

Am I missing anything?