It comes from the meaning of the words and etymology of what they meant when they were first used, not their modern usage. Imputation means that one is only ASCRIBED the righteousness. They aren't transformed:
1540s, noun of action from
impute (v.) on model of Middle French imputation, or else from Late Latin imputationem (nominative imputatio) "a charge, an account," noun of action from Latin imputare "to charge, ascribe."
If I imputed my debts to you, would that mean that you did anything to earn them or that they were really yours? No. It means that the reputation of those debts are ascribed to you. This happens a lot in modern Credit Bureaus, where people get bad credit scores because someone who has the same name as them has a lot of debt. In one case, a person was denied an apartment because a miscommunication in one of the credit bureaus labeled, or imputed, the title of terrorist to him, and the actual terrorist in question was both dead and didn't even have the same name as he did.
That is what imputation is. That is what it meant when it was first being used. Sure, you've modernized it, but that doesn't change its etymology. This is what it meant when it was first being used in the Reformation. You can't escape the meaning of a word simply because you use it differently. The people who first coined the term used it this way. This is why Orthodox reject the term altogether. The meaning of words is very important, especially for a person like me, an interpreter between languages. It has been my job to understand words and their meanings. So when you come at me with a word like Imputation and get surprised when I realize that it shares the same etymology as reputation, being from the same language with the same root word "Putare", then you're looking for a ballgame that's not in your league.
Moving on...
Since Romans says we are not justified by works OF THE LAW, and James says we are justified by works, and not by faith alone, then either James is speaking of some other kind of works, or either James or Paul are talking of the same thing and one is wrong. See, your Romans Switchback doesn't really help you here because it ignores the whole of Romans for a simpler, easier salvation that is really just spiritual fire insurance. That's all OSAS is in the end. Fire insurance. If there is literally nothing you can do, even of your own free will, to give up salvation, then you:
1. Do not really have free will, but are forced to do things against your will.
2. Do not need to worry about a thing. Eat, drink, and be merry, for even if tomorrow you die, you still get eternity in heaven, because that's all that really matters.
That last one is pretty much perfectly summed up in the most common question I hear at invitations in Protestant services. I heard this phrase so many times at Tennessee Temple University, West Jacksonville Baptist Church, Highland Park Baptist Church, and every other Baptist church I have been in, from so many different pastors, I wondered if someone had printed the question into their Bibles somewhere:
"If you died today, do you know if you would be in heaven?"
or
"If you died today and God asked you 'why should I let you into My heaven?' what would you say?"
The questions center upon the final destination, and not the final relationship.
To be quite frank, if I had to go to hell itself in order to spend eternity with Christ, the price of hell would be cheap compared to the benefits of the relationship with Christ. I really don't like the idea of hell, but if that is where I would be if I had a relationship with Christ, then sobeit. I'll take hell with Christ over heaven without.
Salvation, for the Orthodox, has nothing to do with the where. God is everywhere present and filling all things. Saying there is a place God is not is like saying that there's a place where nothing exists at all. Even total vacuum is filled with virtual particles popping in and out of existence at all times. That's just how God created the universe. For me, being saved is knowing everything there is to know about Christ, in the same way that a husband knows his wife, not as a list of facts about her, but as a lifetime of experiences, an eternity of experiences with Him.
This is the reason that salvation is never OSAS for the Orthodox, because the very meaning of salvation is fundamentally different. For the Orthodox, whether we go to heaven is immaterial. It's a consequence of the relationship, not the goal of the relationship.
The Bible says you shall know them by their fruit.