Oi replikmaster, sou brasileiro também!
I say do not worry about the hands getting loose by removing and reinstalling them. I've done this several times with many of my watches, big bangs included, and I have never had one single problem. What should worry you instead is breaking off the post of the chronograph minute counter wheel. This wheel - along with others - has to be removed when you swap the date wheels, and breaking its post is very easy. I myself have managed to break two of those, but I also managed to fix them using hypodermic syringes. Having the appropriate tools to remove the gears involved in transferring the minute counter from 12h to 3h is a must, but even then it is risky because the gears lie in difficult to reach positions. Your watchsmith - and you - should be aware of this potential problem.
If you don't mind me giving you a hint, try and apply a tiny drop of oil to the wheels' posts a few minutes before removing them. This procedure might alleviate the risk of breaking off the posts. When reassembling the gears, carefully clean the posts to remove the oil.
Agora uma curiosidade: vc nunca teve problemas com alfândega brasileira? Ou tem algum esquema?
