Bring It

In the previous post we discussed the Meshech Chachma's approach to understanding יביא אותו.  The Seforno takes the same basic approach of יביא עצמו.  He explains that normally for a change to be affected in a person they need someone else to bring them to what will effect the change.  The nazir on the other hand, is different, for he has reached such heights that here is no need, indeed no one capable of raising him.  However, there are other interpretations from the Rishonim in the verse.
The Even Ezra (and Rashbam) explains differently.  He says או: יביא הכהן אותו – בציווי בעל כרחו, להקריב את קרבנו.  The possuk means that the kohan should force him to bring his korbanot.  This would seem to based off the Gemorah in Arachin (21a.)
The Mishna in Arachin (21a) says that we force a person to bring a korban olah but not a korban chatas.  The difference is that we assume a person will come around to bring their chatas in order to obtain atonement.  The Gemorah says that the to offer the chatas of a nazir, which a person may be lax in offering for it doesn't withhold the completion of the nezurit, we will also be forced the person to bring it.
The Ramban in Bava Metzia (3b) brings a proof from the law of אין ממשכנין that the obligation of the chatas is dependent on the person's own knowledge of what s/he did and hence one will even be believed against witnesses to determine if they are obligated in a chatas.  What is his proof,  the reason we don't force the person if practical because the person will end up bringing the korban to obtain kapparah, not because of a lomdus?  And the practical reason is accepted by the Ramban himself in Bava Basra (48,) Milchamos Bava Kama (36b, 18 in daffay haRif,) and seems to be supported from the Gemorah in Bava Kama (40a)?
In every obligation to bring a korban, there is both a mitvah obligation that one is commanded to offer the korban and a monetary obligation to pay the korban to hekdesh (see Kiddushin 13a.)  Both of these obligations are reason enough to force someone to offer their korban.  The Briskor Rav in Arachin shows that indeed it is a machlokes Rishonim as to what din is the cause to force one to bring the olah; to do their mitzvah (see for example Ketubot 86,) or because of the שיעבוד ממוני that exists upon the individual to pay their korban.  Based upon this we can possibly understand the Ramban,  The practical reason is why we don't force the person to bring the korban of the monetary obligation; they will end up doing it.  However, the mitzvah obligation should still require him/her to be forced to bring the korban; it is from there that the Ramban sees that a chatas is dependent on the person wanting to bring the korban.
The opinion of Tosfos in Rosh Hashana (6a) is that after 3 regalim even by a regular chatas we force the person to bring his korban because of the violation of בל תאחר.  Asks the Keren Orah in Nazir, if so, when it comes to the chatas of the nazir of course we should force him to bring it because there is בל תאחר immediately (see Tosfos Nazir (4a))?   
Rav Solevetchik (Igrot HaGrid pg. 197) explains that what בל תאחר tells us is that that after 3 regalim is payday, its time that you must pay your korban.  Tosfos holds when it comes payday, you must be forced to pay your dues.  That is for the בל תאחר of korbanot.  The בל תאחר one violates in Nazir immediately is because the korbanot are a completion of the nezirut, as part of the acceptance of nezurit is to to bring the korbanot of the nezurit as well.  However, this is because of the mitzvah, not because of a monetary obligation and that would not be reason to force the offering to be brought.  Hence, there is a chiddush of the Gemorah in Arachin to force a person to korbanot.
The Ramban in Milchamos Bava Kama (ibid) also suggests that after 3 regalim the individual will be forced to offer their korban chatas.  However, the Ramban compares it to the din of forcing to fulfill a mitzvah, nor because of paying a debt, so the question is back, the בל תאחר of nezirut should be the same mitzvah?
[However, Tosfos in Rosh Hashana  ד"ה יקריב also understands the law of enforcing the bringing of the korban is because of the mitzvah and doesn't hold there is a special din of enforcing here, עיי"ש וצ"ע.]