The tactics themselves would be used in combat in sort of a live turn-based system where the player can enter a tactic to use every so many seconds. Indecision will basically cause rounds to pass with the player not reacting. Usage of the tactics award skill points to the skills required on the tactic scroll, roughly equal to the ratio of the required skills (the higher the requirement of the tactic, the higher the reward for that skill). The tactic scrolls' usage would scale with the player's skill levels, so no "Fireball I", "Fireball II", etc. However, the tactics can be traded, sold, found from killing monsters, quest rewards, story rewards, created through crafting, etc. So they would basically be collectible. Some may be considered rare and cannot be traded, but the majority I envision could be. Maybe players could only queue up a certain number of tactics of which they can use in combat at a time, giving the game a Guild Wars style feeling of selecting which abilities are appropriate for certain situations.
I have been thinking about the impact of a system like this. The more I think about it, the more I think queuing a certain number of tactics would help to prevent wealthier players from having a huge advantage in PvP by overwhelming the poorer player with sheer ability count. While one player may have 120 tactics and another player has 24, both can only bring in maybe 8.
So what do you think? And thanks for reading and any feedback!
EDIT: The only other game I know of like this is Phantasy Star Online Episode III for the GameCube, which did decently but was short-lived due to few people having a reason to have the GCN internet adapter (there was only 1 other online game for the GCN) and some other technical issues. There may be some other examples of this type of game elsewhere in the form of F2P games that I am unaware of.