The Mishneh Torah, Hilchot Ishut 3:21 writes that though “the children of Israel have accustomed themselves to betroth with money or its equivalent… if a man wants to betroth with a document, he may do so.” The Shulchan Aruch (Even HaEzer 32:1), echoing the language of the Rambam’s Hilchot Ishut 3:3-4, details the nature of the document that can be used for kiddushin: “He [uses] paper or pottery shard, even if [the paper’s value] is not equal to a peruta, and writes for her, “Behold, you are betrothed to me,” and gives it to her before witnesses, and he needs to write it in the name of the woman to be dedicated [ha-isha hamikudeshet], as one would in a get….”
There isn’t a lot of detail in the sources (at least the ones I’ve encountered–please comment if you know something) about what is forbidden to write on such a document so long as the above requirements are met. As such, the shtar [document] of kiddushin could be framed as a parallel document to the ketubah, in which the bride promises not only monogamy, but also to feed, shelter, care for her groom and what the financial (and possibly legal) implications of the marriage dissolving might be. In such a case, the standard ketubah would only require a clause promising the groom’s monogamy for the parallel to be complete.
In this solution, the groom would effect kiddushin by handing the bride the document detailing her responsibilities—or she could accept it through kinyan sudar[acquiring through taking up an object] with a scarf or pen—and the bride would hand the groom perhaps the ketubah and a scarf or pen, thereby effecting the kinyan through which his ketubah responsibilities are acquired. If the couple wished to do an exchange of rings, they could do so after this, to be clear that shtar [a document], not kesef [money/a ring], is the means of acquisition.
This solution has the advantage of being kosher kiddushin, and for having parallel responsibilities or promises “sold” in the respective documents—there are two kinyanim, one representing each party’s “selling.” It lacks, perhaps, the romantic or “traditional” feeling of a ring being used to effect kinyan, but of course avoids that method’s many drawbacks.
Unfortunately, with this solution, the groom is still the only party engaging in acquisition—he acquires the bride (or at least her sexuality and other ketubah-like promises) through kiddushin, and then acquires the responsibilities of his own ketubah through kinyan sudar. Though the bride’s level of participation and responsibility is much more on par with the groom’s level, he is still fundamentally the actor in this drama. Please see the article by R. Dov Linzer for more information on some of the underlying concepts, here.
ADVANTAGES: Halakhic kiddushin, enables bride and groom responsibilities to be relatively parallel, makes the ring-for-ketubah exchange of the Linzer model much more parallel.
DISADVANTAGES: Doesn’t “feel” like traditional kiddushin and the ring exchange, the woman is still technically acquired, couples lose the opportunity to detail each party’s responsibility to the other in one ketubah, one single document.