Tips for brewing stations in the Nether
Solution 1:
In 5 hours, when 1.3 is out, I guess you could fill an ender chest with water buckets when you're in the overworld. Place another ender chest close to your brewing stand and you're all set.
Solution 2:
It really depends on how you play minecraft. The tricky thing about brewing potions isn't just that you can't really produce water in the nether, it's that your netherwort will NOT GROW unless you're in the nether (and the chunk it's planted in is loaded). That my friend, is the issue.
You have two solutions in my eyes.
You can do what your already doing with buckets and cauldrons (this is what I do). But to further make your life easier, you can build a portal very near your brewing station. (build the portal on the nether side) Go through the portal (you should now be in the real world) and dig a hole 1 block deep, 2 blocks wide and 2 blocks long. Put a water source in each opposite corner of the hole and you will have an endless watering hole to easily fill your buckets back up and jump right through the portal back to your station.
You can do all your brewing in the real world (nothing is stopping you) - The only problem is your going to have to find some reason to spend time in the nether to let your netherwort grow. I suggest you build an underground chamber in the Nether, plant a LOT of netherwort, and spend a few hours or so building something cool, or killing zombie pigman, or doing both maybe. If you grow enough netherwort, such as a room of it 20blocks x 20 blocks, That will likely be more than enough to last you several weeks. The stuff lasts quite some time, unless of course you drink your potions like candy.