Penalties for breach are put into a contract precisely because one party can destroy the agreement without the consent of the other.
For how long?
Just like any other ongoing contract, consent is also ongoing. It's not a one time thing, where you consent once at the beginning and must go on performing the contract forever based on that single moment.
What does a penalty have to do with consent, and who's talking about feelings? If a couple wants to establish penalties in the case of one of them withdrawing his or her consent to be married in the future, they're perfectly free to do that.
What you think the terms of the marriage should be has nothing to do with the level of consent required (either on an "is" or "should be" basis) to create/maintain/end a marriage.
Besides, instituting the penalties you seem to want wouldn't change the fact that only one spouse is withdrawing consent to be married.
The simple fact remains that if mutual consent is required to establish or maintain something, then by its very nature, unilateral withdrawal of consent destroys that thing. When one party no longer consents, it is impossible to have mutual consent.
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