Mishnah Kiddushin Chapter 3 and subsequent halakha make it clear that it’s possible to betroth someone on a condition (tnai). For example:
Mishnah Kiddushin 3:2
If one says to a woman. “Behold, you are betrothed to me on condition that I give you two hundred zuz,” she is betrothed, and he must give it. “On condition that I give you [two hundred zuz] within thirty days from now”: if he gives her within thirty days, she is betrothed; if not, she is not betrothed. “On condition that I have two hundred zuz,” she is betrothed, providing he has [two hundred zuz]. “On condition that I show you two hundred zuz,” she is betrothed, and he must show her. But if he shows her [money lying] on the table, she is not betrothed.
Mishnah Kiddushin 3:3
[If he says to her "Be betrothed to me] on condition that I own a bet kor of land”, she is betrothed, providing he does own it. “On condition that I own it in such and such a place”, if he owns it there she is betrothed, but if not she is not betrothed. “On condition that I show you a bet kor of land,” she is betrothed,
providing that he does show it to her. But if he shows it to her in a plain [ie land that is not his], she is not betrothed.
A number of people have taken this idea and run with it, designing traditional kiddushin on specific conditions relating to the kiddushin itself. Often the couple will sign a document (separate from the ketubah) before the ceremony stating something like, “I, (name of groom), indend to betroth (name of bride) on (date), and this betrothal is dependent upon the following conditions:” and then all and any possible terms of the kiddushin can be laid out. Possible terms could be: that I do not refuse your request for a get, or this kiddushin is rendered null and void; that if I do not grant you a get within three months of a civil marriage, this kiddushin is rendered null and void…. and other ideas in that vein. With this sort of condition built in, a marriage could be retroactively nullified in the event that get issues come up. (This idea is similar to the ketubah authored by Dr. Aryeh Cohen, and the conditions offered by the French and Turkish rabbinate in the 19th century.)
A couple could set out conditions regarding any possible scenario that they could imagine, add financial terms to the condition or other specific issues relating to the couple and their marriage that they feel is crucial enough that the very existence of the marriage depends upon it. It’s crucial that both bride and groom sign this document along with witnesses, so that everyone’s clear that the bride’s consent to kiddushin hangs upon the presence of these conditions, and that the groom knew about them from the outset, and that his betrothal of her depends on them as well. This signing can be done privately, with the couple and witnesses, or as part of the communal gathering.
Under the chuppah, either the traditional kiddushin formula could be recited with no reference to the conditions signed earlier, or they might be referenced–“Harei at mikudeshet li b’tabat zo ba-tnaiim sh’hiskamnu, k’dat Moshe v’Yisrael,” eg. (“Behold, you are betrothed to me with this ring on the conditions to which we agreed, according to the religion of Moshe and Israel.”) Or, the bride could accept the ring with a statement noting the existence of the conditions, if that’s preferred, to give her more of a voice in the transaction.
This does not address the kinyan problem, but it does negate the problems that a woman might have with a get as the result of traditional kiddushin, and perhaps helps a couple who wants traditional kiddushin to start their marriage on more equal legal footing.
ADVANTAGES: Traditional marriage, addresses the ever-looming get issue in a clean and easy way, makes clear that the marriage takes the woman’s rights into account to some degree, conditions can be personalized to the couple’s needs.
DISADVANTAGES: It’s still kinyan, declarations by the woman under the chuppah have no halakhic significance.