Way back when, it was discovered that changing from Gnomish engy to Gobo Engy was impossible on the same character, so I assumed the same was so for Armor and Weaponsmithing. So I did do some digging around, and the general consensus is that if you drop blacksmithing your still stuck with whatever path you decided.
I just wanted to give a heads up so no one wasted any time on anything..
