Ok apologies, I honestly didn't read all the pages and just wrote my idea.Its possible my idea is very close to yours, I'll look at your idea soon. SKIP to TL;DR at the end if you're like me and hate reading long posts.
Here's an elaboration of my idea, but a couple notes first:
(1) I'm talking about a larger game mechanic than simply making the "sotl" model (i.e. the Tally Ho ship and that other hunter ship model) be useable by players in game. I'm talking about adding a whole new feature to the game meant to overhaul and revitalize guilds.
(2) This would be a lot of work from the dev perspective, but I believe that my proposition (and similar propositions by others) is greatly worth the effort since I see guilds as the ONLY way for the game to maintain a dedicated player base and keep high-level players interested (the other being grinding for legendary items).
OK here's the FULL concept as I envision it:
A new class of ships available exclusively to guilds (say 3 or 4 new "cool" ship models, one of them may or may not be the "sotl" tally ho model, I actually don't particularly care what ship models are used) ... they could follow the same aesthetic as the current sloop/galleon/frigate/brig thing going, though I would recommend using totally new models rather than just a bigger sloop or bigger galleon or whatever. The guild ships could be available from the shipwright or there could be a new random character standing outside near the beach dedicated to guild ships... whatever.
The guild ships have tiers that are objectively better as the tiers increase. The tiers are progressively more expensive in gold and materials but also require a larger and larger number of guild members to unlock the ability to even attempt to build them. So its not just a playstyle difference, but the tier II ship is a clear upgrade from tier I, and tier III is even better and bigger and so on.
Guild ships require a whole guild effort to build. Something kind of akin to clans in Warframe building a solar rail or pooling research, if anyone of ya'll is familiar with that game. The guild leader could initiate a project to build a certain tier guild ship if a certain number of people are in the guild.
I see three possibilities for actually completing the guild ship build that is initiated by the guild leader:
(1) The tier I ship could be built for a reasonable amount of resources that maybe even one person could afford so that if people really want to participate in this whole guild thing, they can at least sail in with a tier I. Tier II and up would cost more money and resources than a single person could accrue, requiring guild members to contribute into a common "pot" towards completion of the ship. This would require the contribution of a critical mass of guild members, though some guild members might obviously contribute more to the ship than others allowing free riders.
(2) All guild ships will need to be constructed from subsections or parts, such as sails, mast, left hull, right hull, forecastle, whatever. A certain tier guild ship will require a certain number of different "parts" to be completed. The individual parts can be constructed by a single member for a large but relatively reasonable cost and they can only make 1 part which goes into a common part pot for the guild. Once enough parts are completed, the ship can be finished. This would ensure that a certain number of active members contribute to the building of the ship and therefore higher tiers would need more members as members can only contribute 1 part each. Again there'd probably be some members beyond the parts threshold that would have a free ride, but this method at least is a better way of ensuring a critical mass of active guild members.
(3) Subsections or parts to the ships could be obtained from guild-centered quest that each require the participation of a certain number of guild members. The quests for higher tier ship parts would require more participating members. This way you can grind for the ships as a team.
There's probably more ways to work this out than the three I listed, but that's just what came to my mind.
Guild ships CANNOT and SHOULD NOT be available to be sailed by individual pirates on the high seas like normal ships. The whole purpose for working toward these ships would be to participate in GUILD EVENTS that are either regularly reoccurring, or available at all times from a specific island (such as the ship pvp from the French and Spanish isles). The events could be guild vs guild svs where two guild sotl ships could fight each other for giggles. Matchmaking could be allowed only for ships of the same tier for balance or just let chaos reign for funsies so large guilds could demolish others for kicks, idc, whatever. The events could also be ship quests that require a guild ship to complete, such as sinking some really brolic fleets that just can't be touched by regular ships, or appear in a specific area of the sea only guild ships can be in, or whatever. The events could be fighting sea monsters (my personal favorite), since sea monsters were, to my understanding, kind of always supposed to be a thing in the game at some point anyway. There's probably more ideas out there.
Guild events should have a drop table of certain new (or old or whatever) legendary/famed/otherwise rare items that could only be obtained through the guild events. The items would be awarded to all members of the crew of the guild ship on completion, or to the whole guild. They don't need to be particularly powerful items, but they should be good enough to be sought after and be unique. They can even be cosmetic items that do not affect game balance (no OP weapons or anything like that). Even if the whole guild is awarded whatever prize, it would be a way for a guild to show its status and achievement as a group by being able to wear a specific hat or what have you for having finished a hard guild quest with a low drop chance. Alternatively the drops could be actual useful weapons too, but I'm just saying that I think guilds would still grind for this even if it was a technically "useless" item such as clothing or a special emblem or whatever because people like exclusive stuff.
Guild ships could be captained only if you have a certain rank in the guild (such as veteran or officer or whatever).
The whole point of all this is to make participation in a guild more rewarding and more objective-based than just helping out your friends or grinding together or accumulating more members just for the heck of it. There's more ways to accomplish this goal than with the way I described or variations of it, but I think that making guilds more relevant through a system of special ships that incorporates new quests or sea monsters or other new content would be a very great way to go about this while still keeping the spirit of POTCO.
I haven't really noticed any major game changes in TLOPO compared to POTCO. I see the devs added some new characters or loot and obviously did a lot of coding with all the server-ide stuff and other stuff im surely not aware of. It would be cool if the people working on TLOPO could inject something truly original and THEIRS into the game, like really make pirates online their game now. It doesn' have to be with this idea, but some kind of major content upgrade seems like the best way to go about this to me. Of course the goal could just be patch all the POTCO bugs but otherwise leave it be and that's fine too, but I'm dreaming big I guess.
TL;DR: Guilds should become more relevant in order to give players more of a reason to join them and to give maxed players something to work towards that involves socializing and teaming up... the way I propose to do this is by creating a new class of ships of the line available only to guilds that are used in guild-only events for unique rewards.