in our Mexican tradition down here many couples want their cultural customs such as the lazo, coins etc, and for each of those presentations their is a padrino, madrina or a couple, so the word padrino connotes persons other than the sponsor required by the rite of the sacrament. There are no requirements for any of those persons who present the bible, rosary, flowers etc. My guess is this sensible custom arose as a way of sharing expense of a wedding among family and friends.
there are also padrinos for first communion, which are not required by canon law, so there are no requirements as such, but in general those should be the baptismal godparents in any case. If they are not some pastors set the same requirement as baptismal or confirmation sponsors, but they are exceeding the demands of canon law in so doing.
formerly the witnesses to a marriage were also those who testified to the parties’ freedom to marry so there was probably a requirement regarding their legal ability to do so. Now that is taken care of in the marriage preparation with the affidavits of free status.