Some truly great ideas here!
In no particular order.
The reason some houses are locked, is because they don't have locations assigned to them. Now, we could go through and just assign all the same basic house models to all the houses, but that'd take time and IMO just pad up the locations array.
I agree there should be a sneak skill (luck's original name was sneak, actually), and that's something CCC's been working on for a while, also.
Regarding scabbards.
Hmm...very hard `engine-wise` to make a scabbard persist (since we'll have to remake all those models), but what we could do is a fake one. I.e., it's hidden when the sword's drawn, but when you sheathe the sword, the sword model is swapped for a sword _and_ scabbard one.
Ditto on changing thrust/slash mode. AFAIK at the moment that's impossible; the game just pulls a random attack animation.
However, I have a couple _very_ vague ideas on how, at least for the player--not for NPCs--we could code something _like_ that. Dunno how much performance it'd drain.
Of course, if you don't care about _looks_, coding the _system_ would be very easy.
:
You'd just not see the animations match up is all. :?
Regarding pierce. Swords already have a pierce attribute which is used for getting around blocks; would be trivial to use that for defeating armor too.
Owning a house has been the dream of many people, and it's certainly doable, though it'd take a fair bit of coding. And adding functionality would be kinda tough.
Adding weight to items is also very easy, though again it'd only really work for the player.
Much of the trouble is, advanced mods require changing the AI, and most AI stuff is in the engine. :