I would do what you said - a main pair for the horns and spot mics/DI on the rhythm section. I usually do a main pair + spots as well.
Is there an audience?
With a traditional live set up of rhythm section on the side of the horns, then you'll need to consider if you want the rhythm section to sound off to the side in the main pair. Listen and adjust position / mic patterns, etc.
If it's not live (no audience), I would try to put the rhythm section in front of the horns, either facing them with the director (if there is one) in between, or all facing forward. Drums & bass in the center, piano and guitar toward opposite sides from each other.
Other points:
-With only a stereo pair on the horns, make sure you place them where you get good balance, while still being close enough to pick up soloists. I picture them being about five feet in front of the saxes, about 8 feet high, pointing down toward the middle row of bones. I'd also try something other than X-Y. You have limited inputs, and with all the DI'd stuff you're going to need some dimension to the stereo pair. Try for a wider spread than XY gives you. Maybe a spaced pair both pointing down. Also, an XY or ORTF pair will have one of the mics point off to the side where the rhythm section might be, which might create the problem I mentioned already. A spaced pair of cardiods flown above pointing down would be my first thought.
-I'd use a stereo pair of OH on the drums, then (obviously) DI the piano & bass. Close-mic the guitar amp. Pan the piano and guitar away from each other, keep the bass in the middle. I'd worry about the sound of too many DI'd instruments. I'd maybe look for a place for the last input you have to be a room mic for the rhythm section, or place the drum OH's in such a way that you get some bleed from their amps.
Let us know how it goes.