Now just a disclaimer this is all in my personal opinion after playing for a little while now, so dont go flaming. However feel free to add onto my suggestion or discuss anything below. I'll try to order from more important to less important, and again this is just in my opinion.
One thing is the lack of diversity when it comes to making money. It's pretty much raids, hydra or Derwen unless you want to donate a huge sum to kill porazdir or dawn/lizarman brutes. This may change depending on when raids 2 will be released and what the drop table is/how common items are. But for now these suggestions mostly cater to diversifying money-making and keeping items holding their value, along with some general QoL.
Guides - The lack of guides on forums was very unhelpful as a new player, not having a clue about certain things such as gear bonuses when wearing a set, or how to go about training skills, what rares are worth getting from caskets etc. It'd be nice if there were more guides, possibly having an incentive such as a sapphire mystery box or donation scroll as a reward for creating solid, thorough guides.
Adding a new zone - At the minute there is extremely minimal incentive to donate until you donate $3000 for Porazdirs. Adding a new zone and npc for diamond or platinum donators would be a mid ground and give people incentive to donate. I'd imagine they would be in the middle of Derwen and Porazdir, or potentially a unique drop table featuring some less common drops such as nex items/justiciar/ancestral at an obviously rare chance. If this were rejected, I'd like to see Derwens get their hp nerfed down to 1000-1200 and them give a boss point on killing them so they are viable - understandably they arent amazing, and they dont require any donator status, but they really arent great to kill at the minute
Dawn drop table - in my eyes adding spirit shields to dawns drop table was a big mistake. the prices took a huge hit and they are worth less than half of what they used to be. Even if there was an option to throw any spirit shield into the well for a chance at a demonic spirit shield, I'd still suggest that at least the spirit shields become rarer from dawn.
Chambers of Xeric - The first crystal falling phase puts me to sleep, it takes all the fun away from raiding when the crystal phase is like 4x longer than it should be. I'd like to see the first crystal falling phase be the same amount of time as the second phase which is much faster. Also, not as important, it would be nice to not have to range the second phase, so you could melee the whole thing.
Magic Well - it would be nice to see some new items being used on the well, such as armadyl as there is such a surplus from boxes. Maybe a chance of 1/25 to get pernix from armadyl. Also as flame gloves are coming into the game with a constant stream and prices are going lower and lower, it would be nice to see new bis gloves, such as razorback gauntlets. Potentially gotten from the well at a 1/15 chance from flame gloves. Also maybe put in an infernal cape for a 1/50 chance at a death cape.
Mystery boxes - So firstly, the lower tier ones like mystery and legendary mystery boxes are utter garbage. they really need something like a $10 scroll at a 1/100 rate or something so they are mildly worth opening. Also it would be nice if mystery boxes and legendary mystery box announcements were removed entirely. Bluntly, no one gives a crap if someone got a vesta skirt from a box or a chaotic staff. It's junk, we don't want to see it. Personally i play with ::togglealert on, to stop seeing this crap, but then i miss all the good loots from sapphire and emerald boxes, which i wouldn't mind seeing.
Nex - It would be nice (if possible) to have a nex (or serverwide) instances where anyone in the clan chat you are in, can join you. It would also be nice to see nex drops buffed a bit and nex cape items added to its drop table. Currently thanks to dawn and porazdir the nex items arent worth a whole lot and nex isnt worth doing.
Just a couple of other notes, I've noticed elite clues are generally really not worth doing considering you can get a lot of steps and it will send you from 30 to 56 wild, which you cant just teleport to. I'd suggest the amount of steps for elites gets changed to between 1-3. Finally, The scythe X special attack is fairly underwhelming for 100% of spec. It would be nice if this was reduced to either 50% - certainly lower than fire twisted bow, as that is only 60% spec and a HUGE increase in dps for that hit.
Thanks if you actually read all these suggestions, and feel free to comment on any of them either agreeing, disagreeing or what you'd alter. Thanks