I'm thinking that the answer to this question is “No” because of an article I found on MSDN that said
InfoPath gets the list of forms that were selected in the Merge Forms dialog box. More than one form can be selected, and forms are processed in an arbitrary order.
but does anyone know of an easy way to specify the order of forms to be merged using standard merge form functionality? If you do, and will share it with me, you'll have my eternal gratitude and who knows, maybe something even more special than that! 😉