So far, I like what I see. 
Viking, Dragoon, and Knight are obviously melee Jobs (with high HP, Strength and Heave Armor I assume). Are they gonna be somehow different, except for their equippable weapons? A command, for example.
Unfortunately to my knowledge there is no way to implement Job commands... However, I have done my very best to differentiate stats for jobs even if they are closely related. Also, different weapon types have unique properties so there is a reason to use one Job over another (depending upon personal preference).
And what about the Job promotion? Since I think it's difficult to think about 12 upgraded versions, I suppose this has been abolished?
Yes. The promoted Job data is what I used to substitute in the custom Jobs so there is no more room for any more data. When I get to that point in the game I will remove the event.
I hope the Bard is in balanced compared to the other Jobs. Sure, for some battles, a certain Job might be absolutely not useful. But it shouldn't be a burden in too many battles, as players will be raging because of being stuck with a Bard forever.
My number 1 priority was making sure every job was equally viable, despite not being able to include any Job commands. For example, the Bard has high Agility combined with Harps that have a chance to inflict a status effect.