by VaultBoy
There are no spoilers in this. All of this is conjecture based on the base rules and components. I have not played it (yet).There are 5 roles, but only 4 pawns. You could pretty easily substitute a pawn if you own standard Pandemic or grab whatever component you want for the 5th player. There's just nothing in the box to represent that player.
I haven't counted, but there have to be at least 10 event cards since that's the max you can have funded per month. The game has you start with 4 in first month and it adjusts based on how well you do. You could potentially start with 6, 8 or even 10 in the first month to slide the difficulty (this is really all On The Brink changes in the rules for 5 players).
Having not played it (I just received it yesterday), I can't say if the game is going to be too brutal with 5. But, like I said, the events will allow some sliding of the difficulty automatically. However, if it turns out you need more than 10 events, you might be hosed.
There is a box of components you open if you're losing too much. It's possible there's something in that box to make it work better with 5.
The biggest problem with 5, that I can see, is if one of the characters is lost. (Their player card is torn up and they play a civilian the rest of the month. Next month they can pick up a new character.) I have no idea if there are any backup roles to handle when there are no roles left to pick. Although, conceivably, losing 2 characters in a 4 player would have the same issue. Lost players could continue as civilians for the remaining months.
Since you can play the game like regular Pandemic before starting Legacy mode, you could evaluate how many events you need to make it play right with 5. If you still find it too difficult, there is box #8 as a last resort to help adjust the difficulty.
It's not built out of the box for 5, so you're going to make some house rules. However, you do get 2 shots at every month in the game. So, if removing 2 events for winning a month in 5 player makes the next month too hard, maybe you house rule it that you only remove 1. But, for losing, maybe you still gain 2.