Hello there Scott, and welcome to Torchmodders, go ahead and make yourself at home, the activity here goes up or down by moments, so if a responce take time just be patience, most of us tend to get busy with RL sometimes, but other times the activity explodes out of the window and it's hard to keep up with everything that gets posted

Now I'll adress some of your questions
1) Transmog. I'd like to see about accomplishing this by one means or another - currently I am using the cosmetic slots mod, and like it alot, however it doesn't cover the hand slots, and its gear doesn't show up in multiplayer.
I think the transmog effect is the not possible for the TL2 engine by normal modding methods, this is because there seems to be no way to have the game alter the looks of an item, this being the mesh (3d model) and/or the texture, even the name is not something that has been possible to change.
Some things are changed dynamically, like a white item becoming green when you enchant it, or the name tags related to affixes of a white item being enchanted, but appart from that not really a way to change those things. Now, don't take my word for it to be impossible, but if it's possible it should need some heavy work on it, since you would need a way for the game to find the name data of the item, and then replace it with something else. I think that someone found that if you can have affixes totally replace the name of an item for an unique name, but this unique name has to be predefined in the affix, so It won't change dynamically.
Now, changing all this, should be possible by hex editing the item data on the shared stash save file, but for this you would need a response from
@Chthon, he is the one that has the most knowlegde on the hex and code editing part of TL2 (that's more hacking than modding if you ask me

) But if you have experience with coding, you could get that working and maybe do a little hack tool like StashNinja, but for changing items appearance and name (nice part of this? would work on vanilla too)
Another thing, I don't know the cosmetic slot mod, or how it's build, but most of the time problems with things not working on MP tend to be related to "Local only" flags not being changed to false, but this is just a wild guess. Other times is just the engine MP code part not interacting properly.
So TL;DR:
A) I doubt it's possible
B) I doubt it's possible to do in a dynamic way, you can brute force it by making item clones of every unique item with different 3d models, and making an unique recipe for every clone, but this is a tone of work, and tedius work for the most part.
C) Could be bad "local only" flags, or an engine malfunction.
Then about the Dread pirate class passive, I'm not really sure if you can tied the chance to proc a skill to the chance to execute, also there seems there is not a "Cast skill on execute" effect to make skills trigger on execute (if someone has input on this it would be great). But I think your first step should be to contact the modder to see if he still want to update his mod, if he doesn't want to work on it anymore, not really a lot of sense in fixing his work.
But about this, better to wait for some of the skill experts around,
@gytfunke @Khazad @TwinkleToes @Phanjam and others to say his piece.
And the last part about the Quest/vendors... not really much to do there, if I remember correctly the camera in TL2 is tied to something like a rail, you can move it up or down the rail to get closer, but I'm not sure if you can "lower" it enough for it to look like a first person view.