Yes, but, if you haven't noticed, I'm trying to get out of you more details on how you envision this to work.
All I have to go off of is, when aiming, you press a button at the exact time, to trigger effect. With how every job is designed, this would mean pressing a GCD to start the aiming process, then pressing a button again to execute. I would assume you do not want the execute to be based off of the GCD timer, otherwise you could, in theory, use the GCD timer itself to queue the exact trigger press, making the idea pointless, or, since you have much higher freedom with oGCDs, you press an oGCD to trigger the effect. If you want to shake up the core foundations of every job, 1. it probably won't go down well and 2. you need to explain how you want to shake it up, how should this system work.
Based on my above understanding, I then questioned how it will interact with certain systems already in place, ie. other oGCDs, Skill Speed etc. Conveniently, you ignore those.
Yes, Continuation probably isn't what you envisioned, I know that. I was merely making the comparison that, Squall from FF8, has a timing for his attacks and limit break, which is similar to what you seem to want to propose, a timed button press and the devs solution to that was continuation. It was to show that the devs idea of making a timed input is making it an oGCD, specifically one that can only be used within the specific GCD window.
As for games with timings, 2 big ones that stick out for me are Devil May Cry 4 and 5 and SoulCalibur. Staring with Devil May Cry, Nero has a mechanic where you press the trigger on hit, and you can get exceed gauge, perfect timing grants full exceed gauge, I was going for them whenever I could. As for SoulCalibur, we are looking at the frame perfect inputs, something I used to spend a lot of time in practice mode to get the timings down so that it became second nature in an actual fight. We also have the aforementioned FF8 where the timings are very very lenient. I have also been a player of a few rhythm games in my time as well.
I am very familiar with perfect timings on inputs, but that is also why I do not think it would fit in FFXIV combat design. It also seems to be the general consensus from others in this thread. So sell it to us. Give us more details, how specifically do you envision it to be implemented in FFXIV, these questions people have, how would you answer them? I suspect your response is going to be something along the lines of, the devs will sort it out, at which point I, again, point to GNB, the perfect opportunity they had, and they didn't do it.
Maybe you have a good idea, who knows, but we won't know unless we get more details.