Duodecim is 2 years before Dissidia? I didn't know that 
As for those additional scenes Nomura said they'll be added (and I'm really slow on the uptake-I didn't realize he was so involved with Duodecim beyond character designs) I assumed he meant more dialog between the characters in Dissidia's game. They mentioned additional dailog before, so I'm guessing it'll be similar with FFXIII where there's all that talking/comments on the field.
There's that frustratingly brilliant plot point about Duodecim-Dissidia: whatever happens in Duodecim will be forgotten in Dissidia for the heroes. For example, if Squall ever finds out Laguna's his dad, he won't remember. Tidus won't remember Jecht was on the good side, and bunch of other stuff I'm sure.

As for those additional scenes Nomura said they'll be added (and I'm really slow on the uptake-I didn't realize he was so involved with Duodecim beyond character designs) I assumed he meant more dialog between the characters in Dissidia's game. They mentioned additional dailog before, so I'm guessing it'll be similar with FFXIII where there's all that talking/comments on the field.
There's that frustratingly brilliant plot point about Duodecim-Dissidia: whatever happens in Duodecim will be forgotten in Dissidia for the heroes. For example, if Squall ever finds out Laguna's his dad, he won't remember. Tidus won't remember Jecht was on the good side, and bunch of other stuff I'm sure.