Is there a way to increase/decrease casting speed?

Solution 1:

I'm pretty sure there aren't any console commands that can do that. But it's actually surprisingly easy to mod it yourself with the Creation Kit. It's all graphical, you don't need to know any programming or worry about anything complicated.

If you're interested, check out CreationKit's tutorial on how to install it, and create, save, and load your first, blank mod.

Then, in the Object Window, expand Magic, and click Spell. From the list you can select the one you want, and double-click to edit it. It should look like this:

Note that by default, "Auto-Calculate" is checked and you'll need to uncheck it, then set your Charge Time down. Then click OK, save, and remember to load it the next time you start your game, and you're done.

Edit: While I did try this out and test it myself, there is one possile caveat that I didn't check for. If my suspicions are correct (I'm new to modding, myself), changing this value here probably means that enemies who have this spell can cast it right back at you just as fast. (Edit 2: Be sure to see kotekzot's response about this)