On Loans, Liens, and Land

Tosafos in Baba Basra 92b brings a machlokes by a loan if the borrower has both money and land must he pay in money or can he pay in land if he so chooses. This is dependent on a sugya in Kesuvos 86a. Tosafos also says that bimakom hefsed one may pay land. Tosafos in Baba Kama 9a also brings this idea of paying land instead of money. The Gra understands this Tosafos as following the opinion that holds in general that land can be paid even when the borrower has money. This he proves from another Tosafos in Baba Metzia on 14a. However, R' Elchonon writes that this is not so. Even according to the opinion that in general when one has money he cannot pay with land. This is not so bimakom hefsed. In case of a loss of money even that opinion holds that land can be paid. See the Kobetz Biurim Os 6 for this discussion.
The Ktzos Hachoshen in Siman 101:5 concludes from the fact that bimakom hefsed one may pay in land that the entire din of paying money first is only a din d'rabbanan.
The Nesivos, however, in Siman 107:4 that the din that one must pay money l'chatchila is a din d'orayssa. However, if the borrower dies and leaves yorshim, so there is no shibud haguf on yorshim and therefore they are not obligated to money l'chatchila. This is actually a bit of an issue because the Nesivos himself in Saif Koton 9 says there is a shibud haguf on yorshim. There is also a Rosh in Gittin 50a that implies this in a discussion about yesomim who are adults and there obligation to pay the debts of their father with idis. While the Nesivos has to dance around these issues in order to explain why yorshim are exempt from paying money, the Ktzos has no such problem. He can just say that paying money l'chatchila is only a din d'rabbanan, and the Rabbis weren't machmir on yorshim. The nesivos also has to deal with why money must be paid only l'chatichala and not bimakom hefsed, whereas the ktzos can easily explain that the Rabbis were lenient bimakom hefsed.
The Ktzos in Siman 116:2 discusses the issue of how you evaluate a field with a lien on it. Some say that we follow the price of the field at the time it is sold. Others say the purchaser always gets the upper hand (see the mechaber there). Finally others (see the Rav Hamagid) seem to hold that we follow the price at the time the land is collected.
The Griz on the Rambam in Hilchos Shechanim explains the issue as follows. Do we say that a lien is maikkar hadin in every sale; i.e. that any sale which will eventually be nullified due to a lender collecting the property, the sale is retroactively null and void. If so, the value should be set at the time of the sale. On the other hand a lien may be an added halacha. The seller accepts upon himself an added responsibility in addition to the sale. If the achrayus is not intrinsically linked to the sale, the valuation of the property could possibly follow the time of the collection.
In the Griz also we seem to be confronted with the issue of land and loans. When a borrower borrows money is there a specific shibud on land or is the original shibud simply on the borrower to pay money. The more we focus the shibud on the land, the easier it is to understand the opinion of those who say that we value the land's worth at the initial time of the sale.
R' Chaim in Ishus 16:25 asks why is a loan called "a denial of shiibud karka" if a loan is really paid up with money. The Grach gives a lomdishe answer regarding the michayav of kefirah of a of a debt. The Rashash in Baba Kama 9a also discusses this. However according to the ktzos, the answer may be more simple. The whole din of paying money l'chatchila is only d'rabbanan. Perhaps on a d'orayssa level, a loan really could be termed kefiras shibud karka.
What we then have according to this is a major machlokes to precisely define the relationship between loans and what kind of shibudim they create.
Although in my notes I see I have understood all these disputes under one umbrella of thought, this appears to be a complex issue and deserves more thought. At the very least, though, it's a good set of maareh mekomos.