We have a Vision 46. 2014 Liveaboard in Caribbean Dec to April. This will be our 5th season 2019 - 2020. Have learned a lot in those years by experience.
I have all the stuff others have recommended. I installed an arch with upgraded rigid solar panels last season Have nearly 600 Watts. Much better power management now. I also installed Lithium batteries for the house bank which re charge more quickly and can be discharged more than Lead acid types. Pricey but worth it including a whole boat inverter/charger from Victron.
We also have a 7kW genset installed below the cockpit sole behind the steering gear which I like as a backup and we use sometimes for having the AC running if its rainy days that the hatches need to stay closed. We started with a small one, Fischer Panda 4.5 kW, installed over the engine in the cupboard in the aft cabin, which was a factory option, don't go with this if offerred. It is noisy in the cabin and under powered. Our boat was in charter for 18 months before we retired and a charterer overloaded it trying to use all 3 AC units at once so we threw it out and installed the Onan/Cummins as described. Much quieter down below and even in the cockpit.
I have power winches all round (5 of them) We are a couple in our late 50's and I also race quite a bit and we are both in good shape but when cruising the electrics are a must have for us frankly. You might regret not having them in a few years.... just a thought.
Despite the winches I also went with simplification on some of the electric stuff.... I did not go with the autotrim system on the winches just simple electric winch in style, manual operation cockpit table, definitely NOT the joystick docking system that is much vaunted by some armchair sailors.
Not sure if its standard on the 42 but I have a bow thruster which I would not be without.
I have roller furling on both head and main sails and an assym with torsion rope roller furling and bowsprit for off wind sailing. However in the Caribbean its usually a little too windy to use it so I am questioning whether we need it. I think in the Med you would probably use it more and the roller furling is a good system. Ours is the Selden one.
Sailing performance is good on our 46 but its not a race boat and is always loaded with spares, water, fuel etc so not quite the speeds you might expect from a similar sized race boat of course. She points well and I can tack through 90 degrees quite easily in most wind conditions.
The other thing I would look at for your Med cruising in a few years is what spares you will need. I carry the obvious stuff like filters, impellers, water pumps, lots of appropriate shackles, cotter pins, etc. Think also about tools since you WILL end up having to fix stuff. A good basic toolkit including drills, soldering irons, electrical multimeter, socket sets, spanners etc etc Also hose clamps/jubilee clips of all sizes, cable ties. If you have electric heads then consider having a spare motor and pump assembly. I have two electric heads and am considering switching one to a manual operation just in case...
We do have a watermaker and use it a lot. Went with Spectra 150. It simply makes life easier and minimizes watering dock/marina time
Think thats about it. Happy if you have any questions. Enjoy your Vision. We love ours and she get's many admiring glances at the dock.
Ian, S/V Kibo