If you want something a bit faster you could always try soloing a brig. That'll give you speed, and maybe some players would give you a wider berth rather than attack if they are not very confident in PvP.
But honestly, what you're looking for is probably not a thing Rare would want to spend dev time on. It would only really apply to a niche player, and would be too unbalanced if it were just faster than everything. Avoiding combat would be far too easy if it were always faster than every ship, and with it being so much smaller it would be harder to target and harder to see at distance, especially when near an island.
I get that it can be frustrating getting sunk, and some days playing solo can be rough. However, I play solo 99% of the time on my sloop and I love it. You just have to take precautions, like selling more often, checking the map and the horizons often, and always being ok with losing loot. I get it, I hate when I do a Veil quest and get challenged for the Athena's Chest at the end by a galleon and a brig at the same time, but that's just part of the game. You win some, you lose some. I am sure that is not helpful or soothing at all, but I think even if you got a super fast no-cannon solo ship, you would still run in to the same problems and be just as frustrated.
The game is a sandbox, so it is what you make it. If losing loot or "progress" is going to be very detrimental to you, then perhaps this might not be a game that improves your quality of life. It's ok to play a bit of something and say "that's not for me" and move on. I tried Dark Souls 2-3 times and really enjoyed parts of it until it just got to be un-fun and annoying, and so I moved on. And that's ok.