Improve sound of direct from board recording?

Is this 2-channel or were you able to multitrack from the subgroups? There's little you can do with a 2-channel tbh

You could at least try juggling it around with a multiband compressor, but unfortunately if the acoustic is the only element that sounds tinny, you will struggle to lose that. One other thing to try would be trying to notch filter out some of the harshness without affecting the rest of the track too much with a parametric EQ.

Create a duplicate of the track. Add a delay of about 20ms to it and detune it by about 6 cents. Pan the original track hard one way, and the delayed/detuned track hard the other. Route them both into a buss and treat it the signal there. Cheap and easy faked up stereo. As far as treating them, I usually do some mixture of the following with obnoxious guitar parts. Band pass the thing at about 80hz and 2500hz. Season to taste. Drop a 12db cut-out right around 250hz. Futz with your parametric EQ until you find the place that clears the part up. Add gentle verb. If you can hear it, it's probably too much. Do something to control transients. Excited acoustic guitar parts are full of pick sounds and other noxious attack bits.

You could try this, but the odds are stacked heavly against you :( Copy the track, a couple of times if necessary. On one of the coppied tracks filter out everything except the guitar, ( as best as possible of course ) now do some radical EQing to try to get some body out of it. Now make an EQ cut in the main track where the ac guitar is the nastiest sounding, not to radical, just enough to tame it so its not as tinny. Now blend the copied thickened up track with the original to taste. You could copy the thickened track again as well and time shift it a little to try and get that double tracked type sound or use one of the doubler plugins. Like i said this might not work but its probably worth a go. Cheers