Sorry for intruding, but I just came across this site. I am a Wisconsin lawyer. I represent lenders and borrowers. I suggest you consult with your own counsel; however, if she or he is experienced, she or he will tell you there is no reason to have a marital purpose statement signed if both parties sign the debt instrument or guaranty. It is not the law. In fact, it is not the law even if only one signs the instrument (other than in connection with certain lending programs designed by the government, like WBA loans).
The marital purpose statement is a safe harbor to ensure that you can reach the marital property of both spouses even if the loan is only with one. Without the statement, the non-obligor could argue that the loan was not in the interests of the marriage or family and, therefore, you can only reach the obligor's 1/2 interest in marital property and the oblifgor's individual property. With a signed statement, the non-obligor loses that argument.
Therefore, if both spouses are obligors, there is no purpose in the statement. Moreover, if you do not get the statement signed, it does not invalidate the debt. All it means is, in some loans, you might not be able to reach the non-obligor's 1/2 interest in marital property. I emphasize might because the non-obligor has to prove that the loan was not in the interests of marriage or family. In fact, the law presumes that all debts are in such interest, but it is rebuttable by the non-obligor. Most credit benefits the family.
Finally, I would suggest that you be careful in saying you always require both spouses to sign guaranties. That is illegal under federal law and can invalidate the guaranty.