The main Grade 3 Vanguard for this deck is Ultimate Lifeform - Cosmo Lord. Reason being is that you can set up the Vanguard Power Lane to have at least 20000 or 25000, due to this card:
With Mashiradroid, you can use Ultimate Lifeform - Cosmo Lord with Mashiradroid as a combination. With a 7000 booster behind Ultimate Lifeform - Cosmo Lord, you have a 20000 Power Lane. With more than one Mashiradroid, you can have Cosmo Lord exceed 20000 and make it 25000.
Since the deck is focused in on heavy Counterblasting, I will recommend that you would use cards when you call them to the Rear Guard Circle, you can unflip damage.
4x Red Lightning
4x Battleraizer (One of these would be your Starting Vanguard)
4x The Gong
4x Wall Boy
4x Clay-doll Mechanic
3x Twin Blader
3x Oasis Girl
4x Hungry Dumpty
4x NGM Prototype
4x Magician Girl Kirara
4x Ultimate Lifeform - Cosmo Lord
4x Muscle Hercules
If you have any questions, thoughts, or comments, leave a comment.