How alt-friendly is this game? That breaks into several things:
1) How many character slots do you get? That could be by default, or the ability to buy more.
2) How viable is it to actually play a lot of alts? The game sounds like it has very long-term progression, but they seem to be claiming it's horizontal progression. There's a huge difference between "you'll be less crippled than in a lot of other games at low level" and actual Guild Wars 1-style horizontal progression where you're the strongest you'll ever be fairly quickly. Is it realistic to make a new character viable quickly and as strong as much older characters, but merely with less versatility? Or are you going to be crippled by being on weak characters if you don't just play one character forever to make it as strong as possible? Having a lot of weaker characters that stay in lower level areas is fine in a PVE game, but a PVE game doesn't seem to be their vision.
3) Do they have quality-of-life things to try to make it easy to split time among alts? For example, do you get shared storage to easily transfer goods? Ability to pass at least some gear back and forth rather than every character needing completely independent, soulbound gear? Ability to switch characters reasonably quickly rather than taking an entire minute to log all the way out of the game and then get back in?
4) Do things that you can buy affect one character only, or all of your characters? Some games have optional subscriptions that affect convenience or power or whatever, but there's an enormous difference between $10/month to get something on all characters on your account and $10/month per character.
I realize that the answers might be "not yet implemented", "still under NDA", or not answerable for various other reasons. But some fans of the game have probably seen a lot more of what the developers have said than I have. If they've said that they're following a philosophy of being accessible to people who like to play a lot of alts, that's very different from if they'll technically allow multiple characters on the same account but promise that game mechanics will punish you severely for using them.