I made the comment just to get a rise and see what direction you were coming from.
I can fully understand your disappointment, and if this is what you want, then leave no stone unturned and do everything in your power to make it happen. There is someone out there who can give you an answer about your real chances, if not this year then maybe next. The trades are Option B for you. Its good to research them also so all your options are open. I have no idea about the remustering before and after, but I guessing, the older you get, the harder it will be to OT as a pilot.
As for an Artillery officer, math skills, spatial perception, and computer skills are important. You start out as a Recce Officer, where you recce a piece of ground, find a suitable location for 6 guns, CPs, and other Bty vehs, bring them in and orientate the guns so they are facing a common direction (Center of Arc). You must always know your map location, and be able to bring survey to the guns. You will have a Recce TSM with you who is always helpful, but the decisions and responsibilities are yours.
After that you are trained in the CP, where you learn Fire Discipline, the theory of indirect, and computation of firing data from the OP to the guns. (This is done by computer and Techs) but no round can go unless you are sure the data is correct. Again you will have a Tech WO to help and guide you, but ultimately you are responsible for rounds down range. And make no mistake, we do not use blanks or training ammunition.
After its training as FOO where you learn the combat team/battle group tactics and learn to call down fire for your supported arms.
That is a very quick synopsis, and I have missed some things and glossed over others, but at least I hope I peeked your interest. Being a Gunner can be rewarding, as we tend to add dignity to what otherwise would be termed an unruly brawl. And you would be joining a proud fraternity, as Once a Gunner, Always a Gunner.
I'll get of my soapbox now.