Good points on your bird, they are cheaply constructed to keep initial cost down, and because they know you are going to crash. People would rather spend under $200.00 for a bird that flys and is repairable alll within those parameters. Versus spending mega dollars for a trainer that's going to cost big bucks to repair when you do thump it, learning to fly.

Now as to your question, sure all the added weight from those repairs and changes in the basic design will definitely affect flight characteristics. Wing can only support so much weight and motor can only push the same. Additional drag will make wing less able to hold the bird up and motor to drive it forward.

Also, look at it this way, the bright side, all those patches/repairs are on the same bird. You didn't have to buy a new bird after each crash. Think how much you saved.