I think it should be up to the players, Cirus, whether they want to play a cohesive, convincing meister/weapon pair themselves or collaborate with someone else... Forcing the second choice just leads to a lot of frustration, especially during fights, like Spriggs said. And, honestly, playing only as a weapon (during fights) just kind of... sucks. 

Unless you're the ultra-rare Giriko/Justin-type Weapon, all you're doing is commenting on the fight, resonating and such. Very little agency, if you catch my drift. What I'm saying is, I know that [i]I[/i] wouldn't want to join if I couldn't have a pair.