Include more shield size options (Full Shield has 50HP, so there could be an option for 40HP, 30HP, 20HP, 10HP and 1HP)
Make "Hold Shield" only lose HP after the shield was hit.
Right now after a reset the shield is already smaller when I reach the opponent so I can't practice full shield break setups. This also makes shield break Tests that need setups like Hero Spells impossible.
Right now "Hold Shield" is pretty useless.
So I have some suggestions: