The long payback would suggest they’re keeping ticket prices low. The ARE makes sense as an improvement in atmosphere not maximising revenue.
There aren’t any corporate seats as such - there’s blocks that get sold with off-site hospitality and that could continue.
Whatever they're called they're still £145 and more and I can't see the club turning them away. The atmosphere might improve but it's the money that matters. A longer payback is more expensive, not less - more interest to pay.
I was going to say, at 20 years it might be because LFC itself is securing the financing, rather than FSG getting a preferential loan deal. But if it's true the payback will be more on a par with the Main Stand, then am I right guessing it's likely increased revenue freed up from paying that off will be directed towards the Anfield Road?
Whatever the outcome it looks good for us. I have a sneaking suspicion ground redevelopment wont stop here, although we might have to wait a bit to see any more. But hey, 10 years with a 62k plus stadium will suit me just fine. 
Normally yes but this is football... as long as the revenue continues, paying the MS back quickly means a happier lender and debt-free income sooner. The club wouldn't want to turn that debt-free income over to pay for the debt on the ARE.
I did always say that whatever is built for each stand should be built to the maximum to avoid being locked into a physical cap on capacity/ have to go back and re-do something - to always have an eye for the future.
My only disappointment in that respect is the corners, where the new stands have been built so far into them, it's probably not worth infilling the corner for the relatively small numbers you'd now get. But then I suspect somebody with an abacus has worked out that balance of cost and benefit... infilling corners would not be cheap.
Redeveloping the Centenary/KD stand would be a massive decision as the Upper is at the maximum angle - you can't add a third tier (an example of not looking to the future). So a total re-build likely
and demolition of relatively newly refurbished houses. Still. Maybe. One day.
As for the Kop, much as everyone would love it, I can't quite see it getting much bigger going back. You could maybe add some rows at the back/ infill the corners but at huge cost per seat and compromise to WBR and the properties there, particularly when the real option could be to add 10,000 safe standing - at which point you might be looking at a 72,000 stadium.
