How/If I'm able to cross-region purchase
Maybe just no-one's been gutsy enough to try this but you could always try installing the shop channel for different regions and see what happens when you log on. If you're points are still there from the last time you added points or it just asks you to create a new account for that region, GREAT, you'll be fine.
When I should add Wii Points
If it has you create a new account for each region then you would only be able to add points in each shop channel you plan to purchase in since the points wouldn't carry over (but you may be able to give game as a "gift" to your other account.) If the points carry over it's probably safer to add points in the chop channel of your home region.
If I can leave with no Wii Points left unspent.
I don't know what you mean by "leave" here. If you're saying "go back to the system menu" or "turn off the console", yes, points you add to your account will stay there until you spend them. They'll be there waiting for you the next time you connect with the shop channel.
If I'd lose any money or games.
- If you're talking about when you "leave" the shop channel, no. The shop channel account remembers what games you've downloaded so you can download them again if you delete them off your console. Points stay on your account until you spend them.
- If you're asking if there's a risk in trying to purchase something out of region, maybe, maybe not. The worst thing I can see them doing is deciding that it's a sure sign that you're a hacker and deleting your account and banning your console. (and voiding your warranty if it's not already void.) In that case I'd assume any points you have on the account would be lost. It would also no longer remember which games you'd downloaded so if you had deleted any that you'd purchased and were no longer in the console or in an SD card, they'd be lost, too.
