You can reuse them I have with no problems. you can get a magnetic drain plug with a gasket cheaper and it would be reusable.
Even if you didnt want to that it would be cheaper that a new Trans. I would change more often as you cant change the filter.
Visually they won't be able to tell but if they want evidence I followed the instructions when changing the fluid, part invoices would be needed. Trading it in with no issues, no problemo.
The issues were supposedly solved with the 21's and up. Only recall is to double check the brake master cylinder torque spec and maybe an SRS seat sensor.