To understand what is going on in this paragraph, we must note what the verses have in common with one another. Thematically, all the verses seem more or less appropriate for a prayer service such as selichot. But there is significant variation between them, and one would be hard pressed to find any consistent pattern based on their content alone.
There is, however, a clear pattern by which we can organize the paragraph; it is linguistic rather than thematic. Each of the first seven verses in the paragraph contains a variation of the verb "lavo", "to come". In five out of seven verses, the verb "lavo" is the first word in the verse. In all seven verses, that verb is arguably the most important word. In this section, "lavo" is a "guiding word" (מילה מנחה), which appears multiple times and is intended to emphasize the linkage between the verses.
This kind of pattern is not limited to the first seven verses. In fact, if you examine the entire paragraph, you will find that every verse includes an important "guiding word" which is shared with the verse before or after. The whole paragraph is a series of units, each of which is defined by its guiding word. That is the basic structure, which unifies the disparate themes which appear throughout the paragraph.
Here is a list of the guiding words found in each verse, along with a count of consecutive verses that include that word.
Yavo'u, yavo, yavo'u, bo'u, navo'ah, bo'u, navo (7)
Barchu, barchu (2)
Romemu, romemu (2)
Vehishtachavu, vehishtachavu, hishtachavu, nishtachaveh (4)
Mi, mi (2)
Gadol, gadol, gadol, gadol, gadol (5)
Mi, mi (2)
Me'ein kamocha, me'ein kamocha (2)
Lecha, lecha, lo (3)
Gevurot, gevurah (2)
Lecha, lecha (2)
Atah, atah, atah, atah, atah (5)
Kodsho, kedoshim, kedoshim (3)
Nekadma, yekadmu (2)
Asher, asher, asher (3)
Haneshama, haneshama (2)
Shimcha, shimcha, shimcha (3)
[Note: Add together the numbers in parenthesis and you will get 51 not 47 verses. This is because 4 verses include two guiding words each, one from the set before, one from the set after.]
In order to understand the larger structure of the paragraph, we can translate the guiding words and list them in order. Then, looking back at the original text to verify that the context is correct, it seems we can divide them into the following three categories:
- Come, bless, exalt, bow
- Who, great, who, unique, yours, greatness, yours, you
- Holy, come, about, soul, name
The first group is an initiation of prayer, the second group discusses God's power and special attributes, the third group discusses God's holy status and "name" as a result of worship by angels and humans. Quite obviously, these three groups parallel the first three brachot of Shemoneh Esreh.
As has been pointed out elsewhere (I heard it from R' Moshe Aberman), the entire structure of selichot - ashrei, kaddish, the stuff in the middle, tachanun, kaddish - is very similar to the structure of a prayer service. We see now that the parallels go much further, since the "stuff in the middle" of selichot parallels Shemoneh Esreh. As discussed above, the long "Shomea tefilah" paragraph at the beginning closely resembles the first three brachot. The repeated sets of 13 attributes in the middle of selichot, each preceded by a complex poetic paragraph, parallel the intermediate brachot of Shemoneh Esreh. The end of slichot, before the tachanun part, consists of a "shma koleinu" paragraph, as well as a "zachor" paragraph requesting the rebuilding of the Temple like in the "retzeh" blessing (granted, "zachor" precedes "shma koleinu" in selichot, while in Shemoneh Esreh the opposite is true).
There is no clear parallel in selichot to the Modim and Sim Shalom blessings. But except for that, the structures of selichot and Shemoneh Esreh are virtually identical.