Ok, so have you AT853 terminated to 3.5 stereo jack? Maybe you already have the mod installed. Disassemble 3.5 jack and look inside if there is a resistor and capacitor. If not, you can install the mod there.
3 wires are reduced to 2 wires in the 3.5 stereo jack (the stereo jack is common to both microphones). And it matters how you do this reduction. You can connect it classically, the third wire will not be connected, you'll let it free. Alternatively, you can connect it in the 4.7 mod, connect the third wire through the resistor and the capacitor to the second wire.
You can make interchangeable cables for the 4.7k mod. Reterminate the mics to the mini xlr. And make two cables, each will have the different connection in the single stereo jack.
mic1 mini xlr -> cable mini xlr \
single stereo jack -> battery box or preamp
mic2 mini xlr -> cable mini xlr /