I have a fretted Furch ABG strung with TI Acousticores.
In the order of your questions:
-No, not yet.
-The acoustic sound of the bass is really good. If possible, maybe making it sound more like an upright bass would have been welcome.

-4 strings
- Yes: Fishman Acoustic Matrix Natural II
quality di straight to the desk/pre
one quality mic (large diaphragm condenser or dynamic) placed about a foot out from the rear of the body, addressing the area below the bridge
(for body, lows) and one small diaphragm condenser, also about a foot from the instrument, addressing the area where the neck meets the body, above the sound hole (for articulation)
and/or:
add one more large diaphragm condenser, directly overhead, at least 3 feet from the instrument/ other mics.
and/or:
add one more large diaphragm condenser, at least 3 feet away from the close mics, addressing the guitar from the front.
you could use all or one of these mic positions with or without the di signal, depending on how it ends up sounding.
you will need to phase check: adjust mic patterns/ proximity...
the final sound of the mics, especially the "room" or distance mics, is going to depend greatly on the acoustic environment. for example, if you want more attack, playing near hard surfaces can help...i've added wood surfaces behind mics to get a bit of first reflection back to the mic. if the room is boomy or has standing waves, you might have to deal with that (changing position, baffling).
for a more upright sound, it's going to be mostly in your approach to playing the instrument (muting, playing clean fingerstyle, or with the thumb).
you also might take 1 large diaphragm condenser, set omni,
and face a corner with the mic in the corner (like robert johnson recordings).
you could also try ribbon/ dynamic mics for any of this.
these techniques have worked for me in the past, but
all or none of this may work for your scenario.... ymmv.
my .02
cheers