A lot of good points here,
such being as some shouts being overpowered, to many shouts to combine, etc such as that.
Well for one obviously you shouldn't be allowed to do ANY 3 word combination to make an ultimate shout, but you should at least be able to mix them up to make some good ones and have some balancing to do with what they do.
Such as my favorite made up one would be 'Aus Ul Bah' or Suffer Eternity Wrath, would probably have an effect of a cripple. It would probably cripple enemies, disarming them, slowing them and them taking damage over time. Could balance it having a larger cooldown.
Another cool one would be "Frul Zun Laas" Which is Temporary Weapon Life, and what that would possibly do is it would make your weapon spring to life, and it would fight on it's own for a short amount of time (Not being able to take damage as, it's a weapon, not a living person, animal or monster)
There are many awesome combinations that we could do but we shouldn't be able to do all of them (most of them really) that would be pure overpowered.
Thanks for your thoughts though guys! Appreciate it
