Just give us the option of instant shouts for the cost of a soul.

So basically you use a shout and you have another one available right away at the cost of a soul. No cooldown.

I imagine you would use em up fairly quickly.

Yep, that would also be pretty fair. Would also make the whole advertised "shouting match with dragons" thing more achievable.

This. Consume Dragon Souls to grant you Constant Active Effects like the "Force Without Effort", "The Fire Within" and "Ethereal Spirit" abilities that buff Dragon Shouts. Maybe even add multiple levels of the effect, so if you really want to buff out something like Fire Breath/Frost Breath to make it useful, you can invest X amount of Dragon Souls to increase your Breath Damage by 25% up to four times. Or maybe even implement a "Thu'um" skill tree that perks are unlocked in through the consumption of Dragon Souls. Completely seperate from normal leveling mechanics, like the Vampire Lord and Werewolf perk trees.