As with so many things that go on in a court room, it may come down to how articulate YOU are.
For example----the mouthpiece may try to say/argue and paint a picture of you as someone who is a gun nut and did all of those improvements to your weapon in order to make it more lethal because your ultimate goal was to be a gun fighter and to kill someone AND you were not satisified with a box stock gun---you had to have a potentially more lethal gun (kind of like "I don't want him just dead, I want him deader!). Same argument applied to your practice. You go to the range twice a month to stay deadly accurate so you can kill.
You have to be articulate enough to not be rattled and explain things clearly and plainly from your perspective. For example, all of that additional work done on that gun were to enhance your ability to protect an innocent 3rd person from danger from the bad guy and/or be better able to protect yourself with a more reliable weapon. If they argue why you can't do that with a box stock gun, you make the argument that you are concerned enough about protecting others and yourself to do what you can to improve your odds of survival and the survival of an innocent 3rd party by having a weapon that will function more reliable. You would not want a potential jam to cost you your life.
Your dedication to practice is again to be able to protect yourself by SHOOTING TO STOP--never shoot to kill. And also by practicing you minimalize your chance of a stray round from your weapon missing the bad guy and striking and innocent person. Therefore all that hard practice is explained as concern about other people's safety as well as your own.
The argument of being such a good shot that you were capable of wounding the bad guy? I was trained to shoot center mass to stop. A shot to an arm or a leg may not stop the threat and innocent lives(including my own) are in danger. An arm or a leg is a small target compared to center mass. By the way, i have never shot a perfect score. So how can you expect me to be a perfect marksman in a shooting?
Again, i want to stop the threat as quickly as possible and reduce the chances for a miss (to injure an innocent) so i shoot the larger target--center mass. Make it a moving target and the reason to shoot center mass become even more clear.
Disable a safety device on your weapon? (BE very carefull here) Jurors are not on the norm gun savy and the only thing that may register with them is A FACTORY INSTALLED/DESIGNED SAFETY DEVICE REMOVED--GUN IS MORE DANGEROUS. I have thought about it such as on a browning hipower and removal of its mag disconnect to improve trigger pull--but i would just rather avoid this argument alltogether and leave all safety devices in place and also avoid the "hair trigger"(you shot my client accidently)argument.
Ammo? I will only carry main stream factory new ammo and not reloads. Avoid the argument of "factory ammo was not deadly enough--you had to brew and make your own more deadly ammo".
What you do outside the courtroom may wind up doing you the most harm. Don't wear the goofy t-shirts that say things like "To hell with 911" and show a pic of a revolver pointing at who ever is reading the shirt. Or the shirt that says "Beware of dog? Best beware of owner!" and shows a pic of a gun. That may be a bit more difficult for you to explain in court as it seems to be more colorful bragging that you are eager/willing to use a gun instead of using it as a last resort and that you may be actually looking for a fight. Be careful as well in your speech around people and friends. Racial slurs and biased talk could come back to haunt you. And never make remarks that you will kill, blow their head off, plant em', etc etc should the "what if" discussions come up among range buddies/friends. They will be under oath to answer any questions about you or what you may had said 18 months ago at that IDPA match.
To sum it all up from my point of view, I will change the grips and sights for better control and accuracy, and perhaps some work to increase reliability(not necessary with my ruger

) --------all in the name of self-defense.
I'll keep the changes to the necessary/minimum to reduce giving a lawyer any points of contention and reduce any questions that could be placed in a juror's mind.
And i will advise my lawyer as to any changes made to my weapon and why. Eliminate the suprises if possible.