As it was alerady pointed out in different thread the Weaponskill progression level were as follows:
Unskilled, Basic, Skilled, Experienced, Refined, Ace, Adept, Expert, Specialist, Master, Grandmaster
Now I don’t believe we had any limitation in getting Grandmaster in all weapons, which I kinda found odd. I don’t think you should be allowed to go Grandmaster in more than 1 and rest let’s say up Ace? Once you are grandmaster with one, and start to use extensively another weapon type and level it beyond Ace, you lose level in your top one as you are natturaly not practicing that weapon but focusing on another.
How you fight with rapire and 2 handed battle axe are two completely different things.
Same similar might be applied for Mages. Specialists in Water should not be able to fully master Fire, eart vs water. So a mage could successfully pick Water and Air spells and wreck havok with them. However his fire and earth magic while still would cause some serious damage, would not be subject of any bonus increases/benefits or perhaps being unbale to learn certain high level spells as they require “Master” skill. (not completely sure this would be practical though, especialy with very small player base)