Comma preceding subordinate clause in the middle of independent clause

I have a case of nested subordinate clauses that are, in addition, separated by a modifying adverb (namely) to help structure the sentence:

Note that we adopt the same stance as [authors] concerning [topic],
    namely that,
        as long as [condition that is fulfilled],
    then the fundamental statements about [X] apply equally to [Y].

My question relates to the second line in the above formatting, i.e., whether it should be

• namely, that, as long as ...,
• namely, that as long as ...,
• namely that, as long as ... or
• namely that as long as....

On the one hand, we have the modifying introductory adverb namely, and on the other hand there’s the interjected subordinate clause beginning with as long as. The adverb potentially needs to be followed by a comma in this case?

Since the innermost subordinate clause is without question closed by a comma, it goes against my inner logician to not use a comma to separate it from its parent clause (though CMOS 6.26 seems to specifically recommend this). Then again, it seems that this might result in an awful lot of commas.

For reference, the version I prefer is the one given in the text snippet, probably because it most closely matches the intended prosody.