Actually, Glaceon lv. X can come into play turn 1 via Broken Time Space and Level Max.
Aside from the glaring Dialga G lv. X issues (weakness and Time Crystal), there are two other problems that plague Glaceon: none of the regular forms have exceptional attacks, nor does the lv. X, and the lv. X's HP is too low, even with the aid of Espeon. This unfortunate combination of poor attacks and low HP means that although the opponent will be slowed down and otherwise disrupted without Powers, you won't be KOing their Pokemon fast enough to prevent them from KOing your Glaceon within a few turns. You can Premier Ball it back, but then you have to get 3 more energy onto the next Glaceon just to do 70 to the active with Avalanche. If the opponent manages to get set up at all before the lock is put into effect, Glaceon is going to struggle a lot. It is also not hard for the opponent to set up enough to deal with Glaceon under the lock, due to Chatot, Cynthia's Feelings, Looker's, the SP engine, etc..
All that being said, I want to experiment with a list that runs Luxray GL lv. X and RR Glaceon. The strategy would be to use Luxray to drag up Claydol, retreat for Glaceon, level up, and begin doing 30 to whatever they're building on the bench. They would have to top deck into Warp Point or Switch to get Claydol back to the bench, or pay its retreat cost, and with Poketurns you could reuse the Luxray to put them in this dilemma repeatedly.