You know i had to check to make sure this thread wasn't super old... Cause a lot of speculation going on here is already confirmed.

Bells are a Ranged/Ammo item, similar to instruments. They cast with them, but are not their primary weapon. This was shown many a time in the JP and NA videos :x.

However, as far as RuneBlade goes, It could simply become another class of greatsword. You know, we have ZWEIHANDERZ or whatever, Blades (Long boring ones), Algol-type, etc... "Runeblade" could be a RUN Specific Great Sword type. I can't imagine that'd be overwhelmingly difficult to program in...

to give more examples

Daggers:
Dagger
Knife
Jambiya
Harpe

Sword:
Scimitar
Blade
Sword
Degen/fleuret

Axe:
Tabar
Axe(Double)
Axe(Single)

Club:
Hammer
Club
Wand

so on, so forth... Basically, adding a new type/class of greatsword that fits the RUN job would be far more likely than a whole new weapon type.