There are a lot of issues it sounds like you have, and frankly they are all important. Wether they are worth doing though is up to you...
1) for the bottom I would go with Baltaplate. It's a hard bottom paint
that after application needs to be burnished. If you are serious about reducing drag it then also needs to be wet sanded. It's a lot of labor so either get ready for sore shoulders or to wright a big check to the yard.
2) replace the main with the biggest roach sail you can fit. I would probably also look at installing a backstay kicker
to allow an even bigger sail. Full batons are required to get something like this to fly right, so the in mast system needs to go.
3) replacing the mast. Unless the larger extrusion came from a multihull
it's probably worthless. Cats and trimarans have vastly different RM curves, and need much stiffer mast sections than a mono of the same size. The mast on my 24' tri for instance is actually a larger section than on my Beneteau
381. If you want to put on a larger mast you need to have someone run the numbers to make sure the new section is large enough, and stiff enough to handle the excess RM of the cat.
The other issue is that multihull
designers tend to undersize sail area for a reason. A mono just heels more and more as it's overpowered giving pretty obvious clues that it's getting overpowered. A multihull however just sails flat until it flips over. By intentionally restricting available sail area a designer
can reduce the likelyhood of this occurring. Of course in performance boats this is pushed, but then you have skilled and watchful crew paying attention to the boat all the time.
If you do go with a larger rig, particularly one this much larger I would really suggest one of two things (if not both) 1) adding load cells and auto trip cleats
to the boat 2) have the NA who does the rig redesign also do a sail plan with wind
speed reef requirements. It is very difficult for most sailors to recognize when a multihull is being pushed hard since from onboard not much really changes.
4) reducing weight - it is always better to reduce weight. How seriously you push this is up to you and the living conditions you are willing to accept. It's usually pretty easy to remove a couple hundred pounds of just trash from a long term cruising
boat, relatively easy to remove more, but with each successive attempt to remove weight it gets harder and harder to find more. So taking off the second dinghy
is easy, but you really do need one. Removing anchors 3-6 is a no brainer but you probably do need at least two. Spare parts
are heavy, but also useful and expensive when away from home so it depends. Cutting off protruding bolts is helpful but only adds up to a few pounds, and is a lot of work. Sanding
away the interior
gel coat may save a few pounds but is messy and incredibly labor intensive.
However all of this will only get you up to whatever the hull
speed of the boat is faster, and make it easier to maintaine. Adding more power won't add much to speed, but will add a lot of load on the boat's fittings. Since I don't know the Snowgoose at all I wouldn't guess what that speed is. But I am sure if you called Prout they would be happy to make some guesses.