The idea is good, but there are better ways.

1. Deflecting the Ice Titan's ice shards gives you about 50tech pts for every time you use Guard. And defeating him also gives XP as well.

2. Defeating Sephiroth is an instant Level-up, no matter what level you are.

Consider this, lets say you need 64000 XP to level up.
Well, no. The XP needed to level up is always < 18000, since Sephiroth gives 18000xp and you instantly level up for beating him.