Here are some concrete suggestions to how fishing could be implemented.
1) Purchase a Rod from the Gem Store
This will unlock the ability to fish in various locations where water is present. Equipping the rod gives you certain abilities.
2) The Abilities
Once you cast, certain interactions begin to randomly shuffle around in the action bar, depending on what the fish is doing. The quicker your response time at doing the right things in the given situations, the greater your chance of reeling in your catch quickly.
You could also require the mouse to be moved around in a specific pattern or to specific points on the screen. Doing so successfully would perhaps lower the time it takes to reel in your catch as well. In order to avoid flailing, the mouse should perhaps be held over a point for a variable amount of time.
A combination of the two might be fun, so if you do well with keeping your mouse in the correct position, the abilities in your action bar will shuffle slightly slower.
Some fish would require very little interaction, while certain rare fish should be much harder to reel in. This would emulate a quiet experience, with sudden bursts of “huge fish!” moments. The more difficult reels would provide better rewards for the effort.
3) The Items and Rewards
Since this would be a gem store unlock, the items reeled in should not provide an advantage, but rather be an alternate way of getting loot. Fish could be used in recipes that either have buffs similar to existing recipes, or buffs that are unusual but unimportant to the gameplay in terms of progression.
Sometimes other types of loot could drop, perhaps at a similar rate to spending ones time running around farming somewhere. This would make fishing an alternative to huge quantities of monster slaying if one needs a break from Orr, while still costing time.
One could also get Karma. Certain fish could be “events”, for example, comparable to running around and randomly stumbling upon events out in the world.
4) Trophies and the Community
Apart from related achievements and titles, a collection of one’s fish should be kept somewhere, perhaps on a board in the home instance. It would then be a collection game in itself to fish them all up.
Each fishing area could also have a fishing NPC that is responsible for that area. He would have a board stating the largest/rarest fish caught in that area (and who caught it), as well as vendor items like lures. Even if it would be possible to fish in all water locations, each zone could have such a character sitting around somewhere. Talking to these NPCs would also provide clues to where in the world certain really rare fish can be caught.
I’m guessing certain fishing areas would attract multiple people who would then hang out and fish together. The recluse fishermen could choose to pack up their gear and go to more remote locations. There’d probably both be a spirit of competition and a desire to help each other with tips and good locations.
5) Additional Items
There could also be a fisherman’s outfit in the Gem Store. The lures previously described could provide a buff that causes fish to be caught at a slightly higher frequency (or slow down the ability shuffle a little bit). There are many fun options for this particular feature.
Certain bait could be used for a chance to catch certain fish more frequently, allowing one to focus more on desired catches. Perhaps there would also be some secret recipes for special bait that allows one a chance to catch really, really rare fish.
I’d quickly smack down some cold cash for a fishing rod that unlocked this