Are you insane?? or are you joking?
What self-respecting trumpeter (or musician) would consider mutilating such a wonderful instrument??
PLEASE do not drill holes in your trumpet. Natural trumpets are expensive, and incredibly "temperamental" (in that the slightest change will make them out of tune... that includes temperature and humidity) and unlike modern trumpets they are a pain to tune.
I take it you play trumpet already...
You know when you play a "D" it is sharp. You can correct that either by pulling out the slide, or adjusting your embouchure.
With a natural trumpet, you need to adjust EVERYTHING with your embouchure and the amount of air you are using.
Try playing a diatonic scale with your mouthpiece... that should be easy. Then try doing it on your trumpet (with open valves). Then FINALLY do it on the natural trumpet.
In the baroque era, there were players who could play a CHROMATIC SCALE!! Though this is practically impossible, that is what you are aiming for.
But dont cheat and get a trumpet with holes... that defeats the purpose of saying "I play natural trumpet." You may as well play a good quality modern instrument.