Already have a vote on the other thread but ok, -1
and not really. Having excess silver isn't a meaningful reason to support this if it effects game balance in the process. That's just spending for the sake of spending. The amount of silver in your bank doesn't mean anything until you use it.
What this proposal does is put those that have been playing a while in a untouchable position more so then now so that those with very little silver have no way of countering them [directly]. Whereas currently you can counter the shield portion by timing it at the right time to attack and the game tells you when this is. If those players thought their defence was high enough to not be breached they wouldn't be using a shield.
The current game design is such that it's impossible to 100% remove yourself from any specific city interaction for an indefinite time period without consequence (disconnected buildings won't do you any good and do more harm then plundering. You have to be online to reset shields and the game advertises when this is). This changes that so instead of delaying when you can be attacked with a slight window of opportunity to instead be that you can never be attacked at all if that's how you wish to utilise the silver as there'd be literal seconds in a random time to do anything.
Only way I could possibly support this proposal is if there's a 24 hr cooldown for the cancelled boost to be locked out of being used again