For if it rested on God as God's sign and God's promise then such would be manifestly casting doubt on the sign of God signifying what God promises.
Have you read Meredith Kline's oath and ordeal articles on the Puritan's Mind main site? I can't agree in full to your reasoning here in this last bit, but Kline will do a much better job than Iof explaining why.
I've actually read this before. Specificially where, I'll check it out, apparently I've missed something. Unless your talking about the whole oath/ordeal as in some receive blessing while hypocrits receive cursing (both having received the sign). If that is the case that has nothing to do with the point regarding REbaptisms. For it is one thing to receive the covenant sign and be a hypocrit already "signed" and then in the end receive greater cursing in that context (in covenant). Quite another to question a second time God's promise via reissuing the sign (rebaptism). And a second, third, etc... rebaptism by definition rejects the prior ones (though I don't believe most laity themselves mean this when they've been wrongly tought by teachers). But back to the point, if the baptism view is from "its God's sign" view, then any rebaptism is in essence casting doubt on God's promise by "asking again" via the sign, "give it to me again." If the baptism view is from "its man/my sign" view, then any rebaptism is in essence merely me saying, "I promise I really mean it this time here's my obedience for You Lord to prove it." (i.e. works salvation and NOT grace which relinquishes especially my works)
No doubt you are the acception to the rule of the baptistic, even the reformed baptist. I've found a few who are not "particular" about the mode, though they argue as if they are. But I've never, personally, run into a baptist who did not agree that the timing of baptism was essential - hence rebaptisms.
So, and I don't want to put words into your mouth, you are saying that timing is not essential to baptism? And you are saying you would never rebaptize? What then is essential such that your understanding differs from infants, professionism? Is that what "validates" a candidates being issued baptism - his/her profession. If so this is still a man centered view of baptism for its warrant rests in the receipant. And it is highly individualistic, actually it is singularly individualistic.
Again, none of this a positive argument for infant baptism as previously stated, but an examination of this doctrine's consistency/inconsistency.
ldh