It’s fine as long as you don’t plan on using your DJI warranty while the drone is still covered.
As for the third party batteries you're considering, it's hard to say how they'll perform compared to DJI's. I wouldn't assume all batteries from...
To properly fix a hole in the skin, especially on the leading edge of a wing, it takes removal and replacement of an entire panel- which has many rivets holding it in place. Once they did that, they would have also have done airframe inspections...