I suppose we can always whip out our new favorite 'cba to deal with it' argument for this query as well, and make it up to the tournament host how they want magic to work. I would strongly recommend a more flexible system, regardless of the prep/time trade-off for better effects (or some other heavy penalty which is where mana would come in.) or you will have an entire tournament full of asshole spellswords, and no one likes spellswords.