Let's build an RPG together.

Pretty much yeah. Mind would be intelligence, wisdom, charisma, etc. Soul could be intuition, sixth sense, awareness? Luck, well, everyone needs a bit of luck every now and then... :P

Or Emotional instead of Spiritual? Emotionally strong people are better at interacting with people and less likely to break mentally.

Yeah, could be something like Ego instead of Soul...

How about naming it in a more visceral way? Something like;

Muscle
Neurons
Glands
Etc.

It's just flavour but might make it stand out.

Another thing to think about; if there's a bit of a body-snatcher thing going trust would be an important factor. Do we need to measure that or do we leave it to the players to RP?

Body: Body is a measure of how strong, enduring and tough you are. It will affect how much you can lift, how hard you can hit, and how much stamina you have.

Move: Move represents agility, dexterity, and reflexes. It makes you quick to act and do so with finesse.

Mind: Mind represents your logical and analytical mind. It is your ability to gather, store, process, and analyze information.

Wit: Wit represents your charisma, presence, and sense of self. It allows you to keep your emotions in check and gives you an advantage in tests of will.

Luck: Luck is simply how lucky you are, d'uh! High luck means things tend to go your way or you tend to end up being at the right place at the right time...

Hmm. Perhaps like Shadows Over Camelot where there can be a (or more) traitor(s) or not in the game? Of course, the GM sort of needs to know who the traitor is, if any... I'm not sure how to handle this with mechanics, really...

There would need to be a rule about how a character would be taken over (which the players would not necessarily know). There could be a selection of possibilities and the one for this game is determined randomly at game start. Something like "the character must be out of contact with other characters for at least five minutes".

that's interesting... One of your party members might be an invader with an immunity to your vision... Certainly changes the tone of the game.

The vision could be a finite resource. Especially if it is drug-fuelled.

It would also leave you vulnerable when you are tripping, so you would only use it if you have a strong suspicion.

Since Wit (maybe rename it Will?) seems to be your "sense of self" attribute, it could play a role in this? But then again, people will automatically suspect the players who put a d4 or d6 in Wit...

Good point, you should be able to resist somehow.

How about a strain meter. It starts at zero and increases when stressful things happen. The higher it is the more likely you are to get infected.

For example, chance of infection could be determined by a d12. Roll a 1 and you're gone. Each point of strain increases the threshold, to 2, then 3, etc. But the GM only rolls under the circumstances defined by the secret rule.

I'm not entirely sure about Luck... Maybe Luck could be something else entirely rather than a attribute, and it could be replaces by Soul (awareness, sixth-sense, intuition) instead? Or maybe we could limit only to 4 attributes from 1d4 to 1d10 and 1d12 would be the domain of a high skill level or other things??

I like luck being a thing, but maybe you're right about doing it a different way. It also makes sense in this type of game to have a Soul stat.

So;
Body
Move
Mind
Will
Soul

(Luck will be implemented some other way...)

distribute 1d4, 1d6, 1d8, 1d10, and 1d12 between the 5 attributes.

Gains X character points to buy skills, advantages/disadvantages.

Skill Level / cost
1d4 / 1
1d6 / 3
1d8 / 6
1d10 / 10
1d12 / 15
(??)

List of skills:
Melee Combat
Ranged combat
Defense
Driving/Piloting
Chemistry
Computers
Security Systems
Demolition/Explosives
Stealth
etc...
(??)

Must beat Average TN of 9?
Difficulty / TN
Trivial / 0
Very Easy / 3
Easy / 6
Average / 9
Difficult / 12
Very Difficult / 15
Insane / 18
(Nearly Impossible / 21??)

how about the alien or entity is a virus? it "possesses" a host, and the hosts are working to make more of their kind and undermine the world governments. and the "Strain" or whatever meter is you measure of your immunity to the virus? people who are weak willed are more susceptible?

Hmm, virus. Some sort of alien/demonic/extra dimensional virus which which possess people and make them work to undermine humanity. Would certainly explain the extremists of just about anything... :P

I really love this idea.

I'm a huge fan of the virus idea as well. Maybe more advanced strains of the virus can even mutate their host, giving them special abilities and even physical deformities (Allows you to implement "monsters" as well as powerful human-ish opponents)

"The Gift"
To see if your character possesses The Gift, roll your Soul die and consult the table below:
8-12: You possess The Gift, you can clearly see the invaders for what they are.
4-9: You have the potential for The Gift. You can see the invaders, but only under the effects of strong mind-altering substances (the substance in question varies from individual to individual). However, when under the influence of the substance, you only see a distorted impression of the invaders, which can be partly explained by your undeveloped gift, and partly because of the trip you are currently having.
1-3: You do not possess The Gift. Who knows why you follow those cooks...