So, I've been tasked with creating an arrangement for 5 guitars (4 electric and an electro-acoustic nylon guitar), piano and percussion for Armando's Rhumba - Chick Corea. I'm supposed to be treating the guitars like a saxophone/trumpet section. I'm not much of a jazz listener, so I don't really know how to translate brass instruments to guitars.
I have some material that I'm using as sort of a guide, but I thought I could ask for some pointers and ideas for anyone who maybe has gone through this. I'll link a guitar pro file that I'm using for writing the thing. We also thought that maybe one of the guitars could take on the bass role. Right now I'm mostly just filling out the chords.

It doesn't need to be a jazz arrangement, although that's what it will probably end up being anyway, and I'll probably won't need to create parts for the piano, but I think it would be nice to have some ideas, since the guitars will be taking most of the melody.
Armando's Rhumba PMC III.gp5
The golden rules of big band horn section arranging.

1. Double the melody at the octave. Don't double anything else.

2. No contrary motion. If the melody moves up in pitch, ALL the other voices must stay the same or ascend as well.

3. Reharm is always fair game, and you can extended the chords however you want.

3a. Don't waste time finding the perfect voicing/extended harmony for every single melody note. This makes the arrangement sound muddy. You are better off just using simple harmony and breaking out the 13ths for moments of impact.

In a phrase: Focus on only the melodic lines. NOT The harmony.

4. You don't need to use chords with names, or a logical chord progresssion. Thad Jones used to just pull notes out of the diminished scale, chord progression be damned.
"There are two styles of music. Good music and bad music." -Duke Ellington

"If you really think about it, the guitar is a pointless instrument." - Robert Fripp
Thanks, Jet.

Also, not even a little contrary motion? ; Since I'm arranging for guitars I guess I can ignore that a little bit, some lines sounded good like that.
And how would you/they go about reharmonizing? I never actually did that. Like tritone substitution? For example, a Db7 in place of the G7? The only thing I did was put a Gaug in place of the G7 at the end of part A because I liked the sound of it.
You can maybe throw in a tiny bit, but it is imperative that you don't lose the focus on the main melody.

Creating a counter melody will take that focus away. I know it sounds horrifically restricting, but if you listen to Ellington/Strayhorn and Thad Jones, who created some of the wildest horn lines ever, everything is parallel.

You don't have to make them all move by the same interval. If the melody goes up by a fifth, the other notes can do seconds or thirds or octaves or whatever. Or not move at all. As long as they don't go down.

As far as harmonization goes, with a five piece the standard practice is to have two instruments doubling the melody an octave apart, and three harmony lines.

With reharmonization, you can certainly reharmonize the main chords in a way as you suggested, but you can also be adding many chords into the line. For example.

The first two chord's of Armando's, IIRC, are Cm7 and D7. However, you have more than one note in the first bar. There's no reason you can't make your lines spell this out.

Cm7 - C7 - B7 - Bb13 - Ebmaj7 - D7

With the first 5 chords matching the 5 notes in bar 1. Now, that follows a logical chord progression, but you don't have to. You could take the pitch collection of a pentatonic scale, MM shade, or diminished scale and freely use those notes.

The other aspect of reharmonizing would be to actually change the main chords of the song instead of/in addition to adding new chords in with your horn lines. The trick is to think about supporting the melody and not bog the arrangement down with a massive "perfectly" voiced/extended harmony for each note. It weighs you down.

When picking chords just remember these three basic rules of reharm.

1. Any note can be any chord tone (1 3 5 7 b9 9 #9 11 #11 #5 b13 13) of any appropriate chord, with a little finesse.

2. Ay chord can be preceded by its dominant or Sub V (the dominant 7th a half step above)

3. Any chord can be swapped out with a chord that behaves the same way.

#2 is what you know as tritone substitution, but it can be really helpful to think about it as dominants with a half step resolution instead of thinking about switching the tritones out with the "vanilla" dominant. This allows you to add them when there aren't any dominants to switch out. Start thinking about SubV's as their own unit and not a replacement for something else.

If that makes sense...

A good rule of thumb for number 3 is to lump all the chords into three categories, depending on what key you are in.

1. Chords without scale degree 4
2. Chords with scale degree 4
3. Dominant chords (not necessarily dominant 7ths, but any chords with a dominant tritone)

Now BEFORE the other jazz guys come after me with torch and pitchfork, you should know these are all MASSIVE sweeping generalizations and that there is way more to reharm than this, but this is a good starting point to begin experimenting with.

I do plan on doing a JTJ about this topic (that will most likely require 10 posts), but in the meantime, ask as many questions as you need.
"There are two styles of music. Good music and bad music." -Duke Ellington

"If you really think about it, the guitar is a pointless instrument." - Robert Fripp
I thought I'd add in a few basic voicing techniques to get you started. When harmonizing to a chord and the melody note is a chord tone, follow this rule (called a 4 way closed voicing):

1 (Melody note), 7, 5 ,3 (All of these are going downwards in a vertical stack)

3 (Melody note), 1, 7, 5

5 (Melody note), 3, 1 ,7

7 (Melody note), 5, 3, 1

For 5 voices, double the melody.
For extensions, you can sub a 1 for a 9, a 6 or #11 for a 5.
But the 3 and 7 must remain unless the chord is a suspended chord, in that case you can sub the 3 for a 4 or 2. Again I'm being sweepingly general. The rules are actually a lot more complicated than this. I can't exactly teach you Jazz arranging over a quick post, haha.

You can also drop voices, when you want a sound that is not a closed voicing. For example moving the second voice to the bottom or the third voice to bottom.
So instead of:

7, 5, 3, 1
you have for drop 2
7, 3, 1, 5

or for drop 3
7, 5, 1 ,3

There are obviously a lot more voicing types, but I'll leave you with these for now.

If the note in the melody is not part of the chord, then you are required to use an approach technique. But since Jet and I learnt approach techniques differently, we see the same techniques in a slightly different way. So I won't put it down. But if you get stuck and need help, feel free to ask.
+1. Good stuff Golden.
"There are two styles of music. Good music and bad music." -Duke Ellington

"If you really think about it, the guitar is a pointless instrument." - Robert Fripp
Damn, thanks guys. Guess I won't be bored for the next couple of weeks
I'll see what I can cook up. Also gave a listen to Thad Jones and really liked the stuff! Again, thanks for the advice.