I would be very surprised about that.
You make the decsions for your opponents. There's no reason why you can't make him use coin tokens.
Absolutely. Pretty much the only way I can think of to word the coin token rules to not allow a Possessed player to use them would be to specifically mention Possession in the rules, which just wouldn't happen.
Well, the rules often refer to interactions with specific cards from other sets (e.g. the Dark Ages booklet discusses about 19 ways Ambassador works with Ruins, Knights, etc.) Although I suppose you could argue those are just clarifications of principles inherent in the cards.
I see the logical consistency that Coin Tokens should be no different from Amb, Masq, etc. But this is an entirely new mechanic - those are all Cards, and as far I can tell there has never been a game action you could take that wasn't playing a card, or the result of it. So the designer can designate the location, availability or plane of existence of these coins however he wants, and could treat them as analogous to trashed cards, or VP, if he wanted. Presumably none of us has seen the rules yet.
Of course if Mr Anderson is correct that 515 has spoken on this, that settles that.
Goodbye. Mr Anderson.