As much as I love natural wood on Alembics,the body shape of the MK is just not for me so I would go for the white bass and if I couldn't get on with the colour, (actually I like it and think it looks would look great with my all black bass), I'd get it refinished in a clear coat. As for the extra string, if it is in the way just leave it off. :-)
Or another option since the neck is quite slim would be to get a new 4 string nut, bridge and saddle. Keep the old ones in case you decide to move the bass on in the future.
Jazzyvee