[KMS Summer Update] MapleStory: Nova

What I'm going to do is create another level 15 symbol (before this update comes out), and fuse it with my current one. Would that work?

That might be possible. I tried having a level 2 symbol absorb a level 3 symbol before, and the game gave me a level 3 symbol with 12 EXP (which is how much you need to level a symbol from 1 to 2). Not sure what happens if the symbol that gets absorbed gives more EXP than needed for the other one to level up, though.