You can always find the latest version of nifutils at the niftools.org forums; https://forum.niftools.org/topic/4518-cant-find-nifutilssuite There are a good few tutorials here at DC too about using it. https://www.darkcreations.org/forums/topic/9949-nifskope-collision-meshes-blender-and-more/
You can use the collision from a vanilla mesh but it HAS to be the same approx shape and size...like for most swords you can just use the same primitive rectangle. it wont work for everything though and definitely not custom shapes. if you grab a copy of nifutilssuite linked above it's all you'll need to add colls to nifs (theres even an option to auto generate from the base mesh geom....its not very efficient but works and would do the job while you get more experienced with colls.)
The last project to be made will most likely be Beyond Skyrim itself. BS has always been more of a collection of projects under one banner, very little work has ever been done on unifying the projects into the one mega land that was its original dream. Thras will have an Alinor outpost btw, some Akavir elements "visiting" too most likely.
Thras is relatively small, well planned out and moving along. I'd say Roscrea will be the first to have a full release, Atmora maybe but Thras wont be last. Pre-release?....probably not like how you mean. Thras is about the size of some of the larger provinces planned pre-releases in total Content that introduces Thras, possibly a piece of Thras... probably yes....but have to be hush hush on details and all that for now.
"Power base, you mean like a castle or fort or something" Depends on the players style of play, could be a fort or something but could also be (examples) a spy network they build, cornering the market in new Thrassian alchemical ingredients...things that would give the player influence in Thras (eventually) "Survival horror" Yeah more survival horror in the sense of the player surviving what Thras is. I guess like "frostfall" but for monster/mystery island vibe. Plant life wants to eat you so have to figure out a way to harvest them without getting poisoned. That kind of thing along with the whole undead/corruption/Cthulhu madness vide Thras has anyway. It's gonna be fun!
"Friendly" would be a stretch but of course there are NPC's/factions (including Sload) the player can do more then fight with. As mentioned in a previous post the Maormer will have a presence on Thras, there sort of a neutral bridge between the player and the crazy of the Sload initially. While survival horror is a big part of Thras its not all it is. Yes the land is hostile and deadly but the player can survive in it. Once they know how, they can build a power base and become more involved with higher tier game mechanics beyond survival.
I cant give much away at the moment about gameplay except to say we're combining several really cool systems into one master "director" AI. Depending on the players entry point to Thras, style of play and so on, the AI will adapt and "throw" more events at the player based on what they like to do in game. NPC's the same, the new system will allow for dynamic factions that fall/rise with or without the players input. Lots of new game mechanics.... Animated ships, Soad Airships, cannon for both, new book mechanics, new "currency" system, new creatures, worldspace, landsacping, architecture that will all bring new game play elements. A lot more interaction with things in game. Magic: oh boy, lots! New Thrassian schools of magic, we actually have a enough spells to do a teaser video for them...must look into it.
TL:DR Better dynamic AI, lots of new toys, loads of new spells. Slug-men-necromancers, a shedload of undead and Coral.