Hey it's me again, I took a stab at it.
I think the simplest way to look at it is that starting from the third bar in your picture, you essentially just have a prolonged diminished chord (F# A C Eb) that resolves to the tonic four bars later (see line 1 in the picture below). And in g minor, a F# A C Eb dim chord will essentially just function as a D major b9 chord missing its root note, i e the dominant (which we even get to see in the last of the four bars). Everything else that goes on is just decoration with some nice voice leading. It's just that Chopin has chosen to spell the pitches in a way that makes this less apparent.
In line 2 I have written an approximate skeleton of the different inversions of the F# A C Eb chord that are used in the score (you could argue a bit about the exact locations the chord changes in each bar but I hope it gets the point across).
In line 3, I have added the chromatic baseline Chopin actually uses. It could be argued that this baseline is just decoration around the skeleton in line 2.
In line 4, I have changed the spellings to what Chopin used, but as you can see it's the same pitches. A diminished chord using F# A C Eb can as you know also be spelled as Gb A C Eb or F# A C D# etc.
I think this is the simplest way to look at it. But if one wants, one can try to analyze the harmonies that get created as the voices wander within this basic skeleton of a F# A C Eb diminished chord. I don't think there is any one single correct answer here, but I have added one suggestion in line 5; the baseline shows the root note of the chords or the chords one could argue are implied. I have added parantheses around the chords I consider implied that are not actually in the score. Hopefully it's clear that the D->G->Ab and F-Bb-Cb progression is "the same", just transposed.
The Ebmin/Bb to B7 to D7 in the third to fourth bar can also be viewed as a series of mediants. But my preferred way of looking at it is just as chromatic voice leading magic.
To feel this more deeply you could try to play my written examples on the piano while considering my comments. Unfortunately I'm not sure how useful my line 5 chords will be for your roman numeral analysis, as I suck at using that system.
Could you help me with another excerpt of Chopin's G minor Ballade?