I know that they already included a skill line for weapon's but they are already feeling a bit stale. I've tried them all and prefer weapons to staves, so that knocks 2 out, and bows were ok but not my favorite. Two handed although a great skill line, just isn't my play style leaving me with only two skill lines to pick from. Here's just a little something I noticed as I ended the main story quest.

*Spoilers*
After you take the fight to Coldharbor with the help of the Fighter's and Mage's guilds, you will see how unprepared the 2 really were for this. Talking with any of the unnamed "Fighter" or "Mage" NPC's reveals that none of them think they even stand a chance against a Daedric Prince, and for good reason. They are fighting a god.
Even the newly acquired Ayleid King who helps to raise the moral and fighting potential of the Fighter's Guild was ultimately lost in the battle. The only person who seemed confident at all was the guy who lead the mage's Guild assault (forgot his name >.<) and that was more of a reflection of his cocky person than what the guild could actually do. Ultimately it falls upon the player to lead the assault and let the guilds mop up the rest.
But if anything, this assault was eye opening to the guilds. This very well might happen again, and next time they should be prepared.
*end Spoilers*

Elder Scrolls fans of old might remember that magic is broken up into schools. These are Destruction, Conjuration, Alteration, Restoration, Illusion, and Mysticism.
6 schools of magic.
There are also 6 skill lines for weapons, albeit 2 of those are staves.
Doing a bit of substituting, we can remove the 2 staff skill lines and add in Sword, Mace, and Axe skills, while also removing the Sword and Shield skill line (since it now is redundant) theres 3 for 3 skills. The 2 handed (since it is also now a bit redundant) can be replaced with a Shield skill line and Dual Wield can be replaced with Daggers, leaving Bow to add the final weapon skill.

That makes 6 weapons, and 6 schools of magic.

The fighter's guild realized the unorganized, run of the mill sell-swords they were acting like wont cut it if the world is threatened again, and take to expanding on skills with the weapons they prefer to use.
(this is suposed to give that guy using sword and shield a reason to use a Sword as opposed to a Mace. They will now affect your target differently; maybe an Axe adds a passive armor reduction on the target, while a Sword has bonus damage. Daggers might add attack speed (no more crit rating please) while shields can focus on actually attacking, or better yet give bonus spell damage or increase magicka like the Oblivion Sorc class. There can even be a valid reason for using a single sword now instead of a sword and a shield)

The Mage's guild also sense's that what they have been doing to prepare is not enough. History books can tell you a lot, but knowledge only goes so far. At some point, you will be forced to use the knowledge you have obtained. Studies go into determining what the schools of magic even are and what constitutes the difference between an Illusion spell versus an Alteration spell. I know I was a little bummed that such an Elder Scrolls classic (Conjuration magic) was exclusive to the Sorc skills, and this gives the player who focused on Fighter skills first the ability to grab actual casted spells, maybe even giving the non-Sorc players a summoned pet or bound armor.

Of course being the premiere hero of both guilds, they will tell you first and foremost about the plan and send you off to meet teachers for each skill. Insert quest of variable length, and after proving to the master of the skill you are worthy, you gain access to the one you want to train. Of course, you can get all of the skills, but limiting it to those 5 abilities is all the balance I see them needing.

Always fun to hope right?