"Yados" by Kiddusin

The Gemara in Nedarim 6b asks whether it is possible to have yados by kiddushin or not. A yad is a term generally used by neder that refers to our "completing" someone else's words in case they are missing information. The case in the Gemara is where someone says to one woman, Harei At Mekudeshes Li and then turns to another woman and says V'At (and you). If there are yados in kiddushin we "complete" his words and assume that he is trying to marry the second woman as well. Otherwise, we don't.
The Birchas Shmuel in his first siman on Kiddushin brings a question from R' Chaim Soloveitchick on this Gemara from a Gemara in Meseches Kiddushin. The Gemara in Kiddushin on 6a says that one doesn't even have to say Harei At Mekudeshes Li if he is already discussing inyanim of kiddushin with the woman. In other words, if they are asukin b'oso inyan, there is a clear umdana that the kesef he is giving is intended for kiddushin purposes and they are married. If it is true that all you need is an umdana the Gemara in Nedarim is difficult. This is because most of the rishonim there explain in that case in Nedarim 6b that there is in fact a yad mochiach (basically a clear intention) that the man really does intend to marry the second woman as well. If that is the case we have clear knowledge that the man is intending to marry the woman and why do we need to get involved in yados at all? Yados are only used in cases where dibbur, actual speech, is necessary (like by nedarim). Then we need to use yados to decide whether the person actually "said it" or not. By kiddushin, where all you have is umdana, wouldn't it be obvious here that the kiddushin works.
The Birchas Shmuel brings in the name of R' Chaim that you see from here that you can't make an umdana from a lashon by Kiddushin. The Birchas Shmuel elaborates that when it comes to most kinyanim, daas is needed in order to create the "challos". In such cases, umdana would be sufficient to reveal what the person's daas is. However, by kiddushin the umdana of the person's intention is not only part of the challos kinyan, but a part of the maaseh kiddushin as well. This is learnt out from the pasuk of Ki Yikach. By kiddushin one needs to have a maaseh kicha and that means the maaseh needs to clearly demonstrate that the person intends to marry the woman. Thus, the Birchas Shmuel concludes, that by kiddushin one needs either speech or an umdana in order to fulfill this inyan of having a maaseh kicha. However, you cannot have an umdana on the speech.
The Birchas Avraham in Nedarim 6b quotes this Birchas Shmuel and understands him as meaning that if one intends to use dibbur to clarify his actions, he can no longer rely on umdana. Rather, he can only use umdana if he is intending to use it in the first place. Based on this understanding the Birchas Avraham asks a question from Tosafos in Nedarim. Tosafos there says that the whole discussion of yados by kiddushin is only if they weren't asukin b'oso inyan, but if they were then they can rely on that and they don't need yados. The Birchas Avraham asks, that if they are trying to use dibbur, how can they now rely on the umdana of asukin b'oso inyan? He goes on to offer an alternative solution to R' Chaim's original question.
My understanding of R' Chaim's answer, however, is somewhat different than the Birchas Avraham's. R' Chaim wasn't saying that it goes by intention and if you intend to use dibbur you can't use umdana. Rather, R' Chaim was saying that there are two dinim in umdana. First, umdana reveals a person's daas. The question therefore was that isn't the yad mochiach also revealing the person's daas and the kiddushin should be good. However, R' Chaim answered that there is a second din in umdana. Umdana also can define a person's maaseh. In kiddushin, a proper umdana can make a person's maaseh kiddushin into a maaseh kicha. R' Chaim also held that a bona fide dibbur can turn a maaseh kiddushin into a maaseh kicha. However, a yad mochiach can only create an umdana in the person's lashon (if you don't hold of yados in kiddushin). In such a case, while it is true that we know the person's intention, the maaseh cannot be defined as a maaseh kicha. In order for the daas of the person to merge with the maaseh and redefine that maaseh you need either a bona fide pronouncement by the person of what he is intending or a bona fide umdana. You can't have an umdana in the person's lashon. While that is enough to reveal the person's daas, it is not enough to redefine his maaseh.
Acc. to this understanding, Tosafos is no problem. Tosafos was simply saying that if you have a bona fide umdana you don't need to worry about yados in kiddushin because the maaseh can be defined by the umdana instead of the dibbur. The fact that the person intended to use dibbur is irrelevant.
Note: After looking into the Birchas Shmuel I found that he does, in fact, describe R' Chaim's sevara as being dependent on the kavana of the mikadesh, as the Birchas Avraham states. Nevertheless, I will keep this post up because I feel the ideas are at least worth considering.