Hi Mark and welcome to the MOA,
The Moody 42 is a slightly more modern take on the Moody 425 we have shared with another couple over the past 14 years and I very much agree with your description.She has served us for cruises between S Britanny and N Holland and never been turned away on grounds of being too big, which, I understand, does happen to yachts of 45 ft or more.
Not all lines are brought aft, the main and genoa halyards are handled at the mast, but are used for bending on and taking off the sails and for adjusting luff tension to suit wind strength. The other control which requires leaving the cockpit is the backstay tensioner, less used in a masthead rig than a fractional, but still relevant. On the 425 we have substantial granny bars to assist work at the mast which I believe the 42 also has.
The in-mast furling works fine if it is properly looked after and the thing lift set correctly before attempting to furl or unfurl. It also benefits from sails in reasonably good condition.Once a mainsail becomes as baggy as an old pillowcase you can guarantee regular jas as the leach gets folds going nto the roll. The other thing to think about is battens which, of course must be vertical. With nobattens you need concave leach (negative roach), with short battens, configured so they do not overlap, you can have a straight leach (zero roach) and with full height battens you can have a convex leach (positive roach) one sailmaker calling his the maxi roach. The last option meas that the lower part of the sail must pack all the battens and the widest part of the sail into the furing chamber, which restricts the weight of cloth and reinforcement at the tack. Best talk with a sailmaker about these choices before buying new sails. When we first bought Wild Thyme, as ex racers we were unconvinced by the in mast furling but now, having learned about it and us being14 years older, we wouldn't be without it, but it needs regular maintenance. I have long been puzzled as to why so many yachtsmen fork out annually for professional maintenance of their auxiliary engines, but rarely spare a thought for the condition of their rig. Furlers warrant annual lubrication and attention with a complete strip and overhaul every 5 - 10 years, whereas most serve 40years with no attention at all until they go wrong.
Your idea to rig an asymmetric furling downwind sail ahead of the forestay is entirely workable. We carry a cruising chute in a sock which is used less than it would be if it were a furling one. Ideally you would fit a short bowsprit to keep the sail clear of the pulpit, 50 cm would be enough, and you would want that stowage to avoid extra berthing fees. You would also want to route the furling line and the tack line back to the cockpit in a way that allows them to be handled by the existing winches.
Peter.
p.s. The Moody 425 is, of course, a better boat and, although I hate to admit it, the Moody 44, which came between the 425 and the 42, is probably the star of the Moody fleet. P.