Mine would be a G&L L-2500 with lightweight empress body, maple fretboard, quartersawn neck, and single-coil mode. For maximum versatility, I'd want either two volume knobs or a blend knob instead of the standard three-way pickup selector switch. This would require going through G&L's Custom Shop.
Why? I love G&L basses with MFD pickups, and occasionally need a five-string. My G&L USA M-2500 is phenomenal, but for a single bass I'd want the L-2500 for its passive operation, additional punch, and available single-coil mode. I'd also want it to be lighter, hence the empress body.
This would essentially combine the advantages of my two fives, the M-2500 and a Sandberg California TT-5 Superlight. The G&L has the quartersawn neck and firepower of MFD humbuckers, while my Sandberg has a lightweight empress body and maple fretboard, operates in passive mode, and offers single-coil tone.