Its not entirely wise for SE just to take one weapon and make a so called "class" to use that weapon and play a certain role but with a bit of freedom from cross-class skills changing the role somewhat. the word class to me seems that your are master of a general type of weapon, not specific like if it were your job. IN the long run they will run into problems with class/job balancement if they do the one weapon per class/job. Take for example gla & pld both use shield-swords. what really is the difference between the two? neither of them are dd's but farily decent tanks, given a certain situation one can solo a bit better and other can help out party bit more but in the end they both are very similar, eventually one will outdue the other with level cap increases, and just over time with new content, one of them will become redundant. Same goes for mrd & war, given a certain situation one will thrive better then the other having the same results like gla/pld.
Its better to have a class that uses many weapons approiate for the THEME of that class like Zyph says. Example you guys want thief,dark knight. The gla class is already a good base, it uses single handed blades which its a master in doing so. SE needs to improve on it by branching more jobs from it, since gla uses shields,swords,daggers, they could add kotestu. the jobs paladin, thief, ninja would extend off it and these jobs will use specific weapons and be a specialist.The mrd class could be known to use 2-handed weapons: Great katana,Great axe, Great swords, Great Hammer, thus corresspoding jobs (warrior, dark knight,samuari,Berseker) branch from mrd class and each job from it using one weapon for a specific task/role. this is the key to the class/job & armoury sytem we have, but it needs to be improved and expanded upon. classes generally are more broad allowing for solo/low man team, jobs thus are meant for full man teams & specific duties. classes will never become redundant or pointless due to their ability for mutiple roles, and jobs will be special and they do their task in a specific mannor no others job could do it in a similar matter.