Policy Additions Endorsements

I handle a several insurance cases where the issue is the validity of endorsements, riders, attachments, added warranties to insurance policies.
The rule is that anything added, attached to the insurance policy, after its issuance, must be countersigned by the insured. Otherwise, any term, condition set forth in these additions, attachments, riders, warranties would not be binding.
The logic is simple.
Without any countersignature by the insured, there would be no evidence that the insured ever agreed to the additional terms and conditions in the riders, attachments, endorsements after the issuance of the policies.
That is fine.
But what if the terms and conditions added are favorable to the insured, but there is no countersignature by the insured.
Can the insured invoke the unsigned terms and condition in the rider, attachment, endorsement?
Can the insurer claim that the endorsement, rider, attachment, added warranties issued after the policy does not have eny effect because the insured did not counter-sign?
Remember in contracts, it takes two to tango.
A contract is a meeting of the minds between two persons.
If there is no evidence of any meeting of minds, i.e. no counter signature, are the endorsmements, riders, attachments, additional warranties binding?
This is the case I am handling right now.
My position is that if the additions to the policies bear no counter-signatures by the insured, they are non-binding.
Thus, if the insurer cannot invoke the terms and conditions contained in additions to policies that bear no counter-signatures of the insured, then too, the insured cannot invoke additions to policies to which he did not counter-sign.
My position is that what is sauce for the goose, should also be the sauce for the gander.
No person should be denied the equal protection of the laws.
Do you agree?