Long winded posts... don't get me started...

I simply feel, for this song, the montuņo is just not in the right mode. A different style, or simply bothering with the I-b7 thing for the verse would be better, rather than just let the one chord run...

Sometimes they work for you, sometimes against. Here, unfortunately IMO, the latter.

I'm also wary about opening up the voicing on trilled brass notes. You listen to most sections, they don't trill chords. Octaves, open chords, yes, rarely whole chords...

It's a good start, and the rhythm could work for you. But the rest of the arranger is working against you, IMO.
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An arranger is just a tool. What matters is what you build with it..!