Thanks for the suggestions - I gave it a fair amount of thought and then went for the unexpected

.
I gave some more thought about what I actually play and the music I make, and realised that while I love the sixties sound of Jamerson et al, and the Maton Master Sound is certainly capable of something approaching that (though McCartney is easier to get, the MS being semi-acoustic), my music is retro-inspired, but not slavishly so. So I took a punt on (gasp!) DA Chromes.
And, to echo the thread that made me think about trying them out: "Holy Cr@p!"
In my original post I said the MS sounded "thin, thin, thin." That was with fairly new DA XL 45-100 roundwounds. I really like these strings on my Spector Legend 4 - bright, crisp, piano-like; a very modern sound that works well for some of my stuff.
But on the MS they were just plain awful, sort of plunky, with minimal sustain and a total lack of (for want of a better word) balls. I honestly wondered if the MS was just a nasty piece of 60s crap luthiery, or whether the damage to the sound board (see below) was terminal. It played fairly nicely, but it sounded terrible.
Put the Chromes on: instant grin. Played a bit more - bigger grin. Maybe it's because the pups were designed at a time when flatwounds were the only game in town, but suddenly the sound had what I can only call authority. It's still surprisingly bright for flatwounds, but the sound has real grunt. I'm getting more sustain (not what I expected), but the initial attack is a punch to the abdomen. For the first time this bass sounds good. Not perfect, but good.
I was given this bass about 30 years ago

. For most of that time it has sat in my closet, unplayed. When I first got it it had a fairly major problem - the bridge had punched through the soundboard, the bass was unplayable, (no, really?) and I was playing different music and fixing it didn't seem a priority. I had other basses.
Eventually after about 10 years I had a rough repair done; the repairer placed a block under the bridge, and it's not bad at all. Obviously not ideal, but quite playable. The repairer told me that in the 70s he saw a few MS basses with exactly the same issue. According to him Maton had underestimated the stresses on the soundboard and had not provided adequate bracing for the top. I was poor; the repair worked. I put it back in the closet and went on playing my other basses, when I wasn't playing guitar. I'd pull it out occasionally, and then I'd put it back.
But putting the Chromes on has made me realise that this bass could sound really good. If it sounds like this in the condition that it is in, how might it sound with a really good rebuild?
I'm going to find out! Back in 2008 I had a complete re-fret and set-up on my 1983 Martin D-28 acoustic guitar. The wizard who revitalised my Martin is a guy named Kevin, who runs Nitrovane Guitars here in Perth, Western Australia
http://www.nitrovaneguitars.com.au/index.html.
If you are ever in WA and you need guitar or bass repairs or set-up, Kevin is the man (he's got a waiting list

, and he's not cheap - the Martin rebuild cost me almost as much as I paid for the guitar new; it was worth every penny).
My Martin is sooooooooo much nicer to play since Kevin did his magic. The intonation is perfect - not just good,
perfect. In any key; try to find a Martin that you can say that about. The tone is far better than it's ever been, and the neck is a joy. Kevin has a pretty impressive line-up of clients, including Cliff Richard, Hank Marvin, Cat Stevens, Michael Vdelli, Eskimo Joe, Motor Ace, Diesel, Tony Gibbs (my former bass teacher), Ian Moss, and a bunch of other people I respect.
So - time to turn this bass into what it can be. It needs some serious work. I figure it needs:
THE CHEAP STUFF:
a fret polish (the frets are fine, just need a little TLC)
truss-rod and nut adjustment.
Clean all electrical components (all the knobs and switches need cleaning, as they click, and/or grind in use).
Pickup adjustment: the bridge pup is really weak in comparison to the neck pup.
Identify and rectify some extraneous rattles, buzzes and squeaks. (The G machine head was a real problem - 30 year-old Blu-Tack stops it rattling, but there's got to be a better way

. The body buzzes might end up in "THE EXPENSIVE STUFF" category but I hope not.
THE EXPENSIVE STUFF:
a sound-board reinforcement; replace the block with proper bracing. (this could be expensive).
Bridge set up and intonation adjustment (at the moment the action is really high - not unplayably so, but not anything that you'd want to play; the intonation is not bad). This could be expensive too, since the bridge appears to be at its lowest possible adjustment. Hopefully this can be fixed with the soundboard repair, as the soundboard seems to be somewhat distorted around the original repair area.
I have no intention of selling this bass, nor do I intend to mess with the finish. It's a 60s bass and it's got what you would expect in the way of wear and tear. That's fine with me. The lacquer is crazed. Somebody was obviously into big belt buckles. It's lived without a case for 30 years. But I intend to rebuild this bass into a working example of fine Australian luthiery.
I'll report back when it's finished. Since Kevin is booked out until January 2011, it might be some time before I get the MS back to full functionality. I'm very hopeful that within 6 months or so I'll be playing this golden oldie, and enjoying it as much as I do my Kevin-enhanced D28.
Cheers!