Just some suggestions that I, personally, would absolutely love to see in the game.

1. Make being a solo viable. There are numerous, numerous MMOs I simply can't play (such as Destiny 2) because you HAVE to be in a group for end-game loot/missions. You should let solos do it, but have it be the same difficulty so that it's just extremely hard. It would also make it an impressive accomplishment if a solo beat a mission that was hard for most 5-man-teams or something. This is my #1 wish and honestly one of my main make-or-brakes for this game.

As a side-note, if you're going to make certain missions REQUIRE a team of a certain size. At LEAST have matchmaking for it and have penalties for people that leave and join games, just to troll. This is another thing destiny 2 doesen't have.

1. Make the combat fun AND challenging. Combat has to be fun. I have more hours than I would like to admit in souls games. The dark souls /elden ring combat works for me. It is always fun and somehow doesen't get repetitive. If the Devs nail this, that'll be a massive W. If there's magic, pleaseeee do more with it than "this spell is a projectile" and "this spell buffs your health for 30 seconds". This is something that fromsoft did great expanding on in elden ring, but I still crave some skyrim-esque spells in a soulslike. That'd be epic. But also naturally the game has to be challenging and difficult to maintain its souls-like title. Don't make it too easy for us!

2. Exploration should pay off. In a lot of open world games these days, there isn't a whole lot the game offers to a player that explores, instead of a player that just fast travels everywhere. On the opposite side, there are games where you spend most of your time exploring, and there's just nothing there. It would be cool if there are field bosses and hidden bosses you can just find when you're strolling about an area, aswell as optional bosses you maybe meet from completing optional story missions.

3. This is by far the least likely to happen, but some amount of base-building would be incredible. Let's say there's a mechanic where you can place a bonfire in an area that's safe as a resting point. Well, it'd be cool if you could "level up" the bonfire to make it more homely, or at least if you could customize it a lot. That'd be awesome.

4. Make the customization cool. Lords of the fallen just released. Customization in that is pretty good. Go above and beyond!!! Add dyes, and maybe even a mechanic where you can show any armour set you want on your character, but the actual weight and stats of the armour you're actually wearing are used practically for defense.

5. Start from level 0. Have respec always available. This is an unlikely one, but it makes sense imo. What do I mean? Well, in the souls games, you always start at a certain level, and there's usually a deprived/wretch class that starts at level 1, with all their stats at 10. So 10 stamina, 10 health, 10 strength e.t.c. this has meant that if you want to min-max a class for, let's say a Dex/str build, you have to use a third-party app to best optimise your class. In an MMO, people would want to optimise their class a lot so they they can be as powerful as possible. So, I vote that there's a "deprived" class, that starts with 0 stats in everything (or 1) and you manually have to put in all the stats. This would allow players to be able to respec on 1 character, aswell as be able to min-max different classes on the same character via respecting. One of the most annoying things about souls PvP is having to make a whole new character on a whole new game and beat every boss again, just so you can start as, let's say a miracle user and be able to min-max everything when you were playing as a pyromancer-user and that wasn't possible before.

6. Invasions. Invasions would be cool. Just as a thing that can always happen. I'd love for this to be a thing in an mmo, but I don't believe it is an any of them. You could do what elden ring does, where, if you're the host, and you have a summon with you, you can be invaded by someone. But if it's just the host, they can't be invaded, or something like that. But soulslikes historically have invasions and that's mostly why I still play games like dark souls 3 and that's got a lot to do with what keeps the community (and the game) alive. If you could somehow make invasions a thing that happens regularly, and not just a "duel game mode" that'd be incredible.

7. Seamless co-op. Lords of the fallen just released. Has seamless co-op. Very epic, especially for a soulslike. So as much seamlessness as possible in this game would be awesome, and also just very much QOL so you don't have to join/rejoin your friend after compete a mission

Niche stuff

Some things that I think the gaming community in general would love you for that isn't too common:

Motion blurr off by default

Add an option to download/install game in 1080p, 1440p, or 4k. A lot of games these days take up a crazy amount of space on people's devices due to 4k textures that are non-optional during installation. If y'all added an option, it'd just be a super nice QOL thing that AAA games still don't do.

Make the performance good. "Oh performance bad? Dead game, I refunded it" is something that is all too common. Even if it takes longer to release or gets delayed. Just make the thing run well and optimise it fully.

Same goes for the load times. If the load times are as fast as they are in, let's say, dark and darker, that'd be absolutely fan-fucking-tastic. ESPECIALLY if it's an mmo where you'll be loading a lot of areas very frequently.

Lots of weapon types, all with some viable options. In souls games, normally there's a few classes of weapons that outshine the rest, and there's even more normally a few weapons that are far better than any other in there class. If you didn't add any "filler" weapons. And made them all good with viable scaling that was hand-tuned and not just determined by some system, that would be absolutely amazing because it's literally never been done before in a soulslike.

It'd also be important in an mmo though tbf, because that would determine the meta. So please don't overlook any weapons, and especially any classes. I'd rather have 100 weapons in total that are all within A Tier than 1,000 weapons that go from S to F tier.

Same goes for magic and stats. If there's pyromancy, lightning, and magic spells, flesh them all out, give them each unique benefits and make them all have a similar number of spells. Don't just let magic have 30 spells and pyromancy only have 10 or something like that.

Some of these are farfetched, ik, but these are just my hopes, alon with some wishful thinking.

Soulslikes are already a massive genre, and for good reason. Combining it with an MMO is a great idea, but due to lots of recent experience with AAA companies not delivering on anything they promised, I can't help but be pessimistic. Nevertheless, if you take into mind what the playerbase feels, y'all can make a kick-ass game that we can have fun kicking-ass in.