First off, I'm typing this out on a tablet so forgive any errors. It's 1am and the coolest room in the house right now is not my bedroom, so no PC access.
Secondly, I don't want this to come across that I'm bashing on the OP's OC, but it is going to seem that way because of the points I'm going to make. Sorry in advance, no offense meant, feel free to logically counter my points.
I'm against alicorn OC's because no matter what excuse you want to toss out, only royalty has been shown as them. We saw how Twilight became one, and it took a very specific thing to be done, and then she still had to be granted alicorn status from the current almighty alicorn princess.
Having an alicorn and then claiming something to specifically make them not op usually only makes them worse. They have traits to make them seem like they aren't op by having things like magic they don't know how to use (or their horn is permanently broken so they can't cast), can't use their wings for reasons unknown, and plenty of other excuses.
I'm not only against alicorns though. If I ran an rp, each character would get looked at and I can tell you there are plenty of OC's that would not get into my groups because of reasons that just go against lore too much.
My lore ocd also makes me cringe when it comes to colors used or designs that look like Discord tossed the pony together in his sleep. I'm also very much against the gun happy, assassin type, emo, loner who is secretly a vampire bat pony that lives beyond the Everfree Forest (to give a mashed up example) because of how out of place that would seem in the show.
Now I'm not saying alicorn or the others that bother me should be banded from all RPs, but the creators of the RP needs to state how lore focused the RP is. That should be what determines if alicorns and assassins would be allowed or not. If the RP takes place in the true to the show world, then it makes sense to screen the OCs and ban alicorns flat out. If its Equestria but Skynet is taking over, then set the gun happy ponies and alicorns free to smoosh the machines.
Forgot to mention that lore friendly unicorn magic is not op. Their magic is normally the universal stuff like telekinesis, and then only stuff that applies to their special talent. Twilight being the exception since her talent is magic, but even then it wasn't op because she had to try hard and learn to cast things. She was shown struggling instead of going "poof the Ursa minor vanishes" and she even admitted to not being able to do certain spells no matter how hard she tried.
ALSO, casting a spell to add wings (temporarily or permanent) does not make a unicorn an alicorn. The show makes it pretty clear that alicorns have their own special magic, they are in a class of their own when it comes to magic. You could chop the wings off an alicorn and they'd still be vastly more powerful than even the highest level unicorn. I doubt unicorn Twilight would ever be able to move a celestial body no matter how much she trained.