Wow. I'm gone for a day and there's lots of new good stuff. I like the passages from the books, and I read up on the "Mask" ability, and you're correct about several things about it. The skill was created for the board game.
"The "Mask" ability was proposed by the Star Wars Roleplaying Game as a method of resolving the debate behind Palpatine's transfiguration during his battle with the Jedi Order. Sources had suggested that Palpatine had been hiding his true features until the battle, and when combined with the damage from the lightning, the result was the disfiguration seen on-screen." (Taken from wookieepedia)
The article does go on to say, however that "It is said that Palpatine, a master at Sith alchemy, may have used this technique in order to conceal his appearance from the people of the Republic and present a more appealing facade. If he did, his encounter with Mace Windu and several other Jedi Masters changed that, when Mace reflected Palpatine's lightning blast back at him, disfiguring the Sith Lord's face."
It says "may have" and "If he did" Nothing canon says that he in fact did use it while the comic "Sithisis" says that he was devoured by a Sith Wyrm and that by killing the Wyrm from the inside, he is able to alter his physical form.
On the subject that Dark side corrupts, again, mater of choice. One would have to choose to abuse the Force. Also, as I posted before, rarely is anyone physically changed by the Force.
" Darth Tyranus and Galen Marek, for example, did not suffer any of the physical degeneration of the dark side, and their eyes only assumed the yellow hue during moments of anger.[24][25] Luke Skywalker suffered none of these effects during his brief bout of intense anger that allowed him to disarm Darth Vader, nor did Kyle Katarn during either of the times that he was (at least partially) driven by the dark side against Jerec and later Desann" (Taken from wookieepedia)
"It should be noted that Sidious's most drastic physical alterations occurred during the lightsaber duel with Jedi Master Mace Windu; Windu having used his own lightsaber to deflect Sidious's Force lightning causing the uncontrolled energy to radically alter Sidious's physical features." (Taken from wookieepedia)
"The worst case of this transformation would be Darth Nihilus, who not only was completely consumed by the dark side mentally but also physically. He had become a living entity of the dark side of the Force and uncaring of all life." (Taken from wookieepedia) What this says to me is that it may break down the body, but what you become after is a physical representation of the Force, so it's not really that your body is destroyed over time, you just become one with the Force.
A theory I have, if you'll allow me. It is said that the Dark side destroys the body of the user over time. I could argue that so does the Light side of the Force. But instead of taking a little piece each time you use it, the Light side waits until you're finished (Dead) and then takes it all at once. And that is why stronger Jedi Masters vanish when they die.
About Sith being evil, the last thing I will say about it is one of my favorite quotes. "Evil is a word used by the ignorant and the weak. The dark side is about survival. It's about unleashing your inner power. It glorifies the strength of the individual."
―Darth Zannah
I admit that I really enjoy this conversation as well and I am looking forward to more of this exchanging ideas in the near future as well.
As for this part you got to admit that some kind “Force Mask” was in place or else yoda as well as every other member of the Jedi Council would have spotted Sidious from the beginning. In a RPG Storyteller Rulebook its always a if and when as well as possibly and maybe since it is a unspoken rule that there are only the rules the gamemaster seems fit so the writers encourage all fantasys with this “maybe´s”.
Even when it may seem differently atm I am not at all someone who likes the idea of unmovable facts of fantasy I love it to play around with them as well as most of the other user enjoy and practice it here. I am just sharing what I was obliged to read in the last decade of Star Wars Roleplaying and I am always very glad to share the “lore” which has been printed down by Lucas Arts and his Partners.
The theory you have shared is very interesting so I thank you for this idea.
Since the Dark Side is able to kill a practitioner and the light side is able to prolong the life “naturally” I would rather think of it a bit differently.
The absorption into the force is for me more like the total enlightment where the Jedi sheds his mortal shell and becomes a being of pure energy which has the ability to share glimpses of its wisdom to the ones on which destiny heeds a higher purpose to bring peace and harmony, wisdom and friendship as well as the possibility of growth instead of any egocentric actions.
The Dark Side can prolong the life expotentially as well (sorry was that written right? ^^) but only to the ends of the practitioners own sake and lust for power and neverending rulership over his victims since he accepts no equals.
"Evil is a word used by the ignorant and the weak. The dark side is about survival. It's about unleashing your inner power. It glorifies the strength of the individual."
―Darth Zannah
Hmpf- I read Rule of the jungle, Eat or get eaten, only rely on yourself, observe everyone who may be a threat.
Nah I don’t want to life like an animal…
For me and my moral compass there are helpful and harmful acts of thought (which most often becomes actions)
BUT!!!!! I believe we are drifting away from fiction into real life and in real life lets face it everyone just wants their peace and freedom with the space compassionately granted by others who are near to express oneself through his individual spleens

Uff that was longer than I thought thank you for bearing with me the whole post!
My best wishes for you!