I had these ideas for the new Arcanum:

1. If you want to use the spells, you need to learn the spells from books or from teachers.

2. Perhaps you need components for your spells.

3. Airships, who will bring you to another countries.

4. Possible to change the amount of Character Points.(Or remove these points.)

5. Possible to change the skin of the PCs and NPCs.

I know the skin one wouldn't work too well. Most characters have a few thousand frames of animation.
The spell components would be anathema to magick in Arcanum. It's based on bending reality to your will. Needing more reality to warp it would defeat the purpose, at least I think so.
Other countries would be incredible, I have to say. I can't imagine how long it might take to build a country in Arcanum, but I think the end would justify the means.
Learning spells from other people seems pretty neat, but might just piss me off in play. If the only way I have to learn a spell like Quench Life is to find some old fart in the mountains way on the other side of Arcanum...I'd just use the character editor and put the spell in.
Changing character points would be odd...The reason they're permanent on your character is to show how you can't actually change who you are by deciding against a past choice.

Now, despite what I've said either for or against your suggestions, I like that you're atually thinking about new stuff for Arcanum.

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What about these ideas:

1. Interior of trains.

2. Interior of airships.

3. Easier to set the startlocation for the backgrounds.

4. Change of the weather, so it starts to rain, snowing, and there is mist.

5. The possibilty to start your own shop, inn, or bar.

6. Farming, or make your own food.

7. Starvation, thirst, or the lost of sanity.

#s 1, 2, & 7:

1) It's possible. Create narrow corridors and add park benches.
This was discussed in the original A:WIP release thread. (Module Discussion)

2) You'd need new interior artwork to make it start to look right. So far no one's been able to duplicate the walls and such like Troika did.

7) It should be possible to script in the effects you described. Hunger or thirst could be done without difficulty. For example: You take a dinghy from the mainland to an island. A heartbeat script attached to the dinghy checks to see if you have water and/or bread with you. If not, it calls for X amount of damage to your health or stamina.
Insanity - I think it's possible, but I don't know how.

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If you can't go through a problem, go over it, under it, or around it.

Insanity could work as a scripted event, pretty much the way Malkavians are handled in VtMB. Would require an insane amount of work though, but if it was only a temporary insanity...

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Lacy: How did I fall in love with such a jerk like him? Why can't I ever meet a nice man?
Tom: You've met lots of nice men, Lacy. I'm a nice man. The biggest lie all of you women tell yourselves is that you like nice men, when, in fact, we bore you silly.
The trouble is, you tell this lie out loud and so damned often that some of us more gullible types hear it growing up and work hard to become nice men.
Well, from all the nice men in the world, Lacy, fuck you very much.