Game doesn't permit taking of actions at appropriate times, even under full control.

For example, I have a land that can cause damage to myself. I have an Essence Cleric in play. If I take damage, Essence Cleric becomes flying. After declaration of combat/attackers by the opponent, I should (prior to choosing blockers) have the option to tap the land, take the damage for drawing the mana, thus triggering the Essence Cleric to become a flyer, thus allowing a block against a flyer.

Futher, this is a wider problem with taking action after attackers are declared.

I had 2 "Get Lost" in my hand. Opponent declared attackers, no option was given to intervene as I had no available blockers.

Even with Full Control enabled, both of these situations still occur the same way. There is no way to take action after attackers are declared UNLESS you have the ability to block the enemy with these cards.