I'm guessing that was a Kenata mod. Some of the things he introduced with his mods have since found their way into the Elemental 'stock' weapon abilities.
I haven't noticed Kenata around since the E:WOM days. I wasn't paying much attention during the E:FE days, so I'm not sure at which point Kenata disappeared. His E:WOM or E:FE Mods might be an interesting place to look for weapon ability ideas.
As for 'Aim', I'd be good with a 5 turn cooldown instead of waiting a turn. As others have pointed out, things can change drastically from one turn to the next, so waiting a turn might be too drastic. If the OP wanted to introduce a couple of bow abilites into his mod, a volley ability, as mentioned above, would also be nice. Dunno if you could design a volley to hit three adjacent opponents (similar to cleave), but I think that would make more sense than 'all opponents on the map'. Didn't someone make a similar ability for the Ranger class?
I'd suggest that 'Aim' increases your accuracy, and perhaps your chance to crit, at the expense of dodge/defense. Essentially, you are standing still, so you are much easier to hit. I'd be wary of a damage bonus, though, as those can easily unbalance things (maybe a small one).
