Doesn't sound like a good idea mang. I took one to a leather shop and they wouldn't do it. You would need a straight punch to get a clean look; to drill it you would have to keep the leather stretched so the drill bit won't wrap up in it.
You need a press punch and some graph paper. JetBlast10 and I did mine as an experiment last year and it turned out pretty good. Just make sure the graph paper doesn't move or you'll double punch some areas like we did. And use a smaller punch then you think you need. If you have a removeable liner I'd suggest you remove it along with your armor so you don't punch holes in them. If you just want a few spots you can have perforated leather sewn in to those areas.