I've been playing this for a long time now and while some suggestions have been added, or at least partially added, I still have some suggestions that in my opinion are much needed features or changes to the game and never got any attention when suggested. I will make a list in order of importance of what for me is needed. Some have been already addressed by other players and I will put them here too.
1- More numbers. If you take a look, we don't have numbers anywhere, it's really hard even for old players to work with assumptions on what the real numbers are on skills, stats and when new patches come, things get even worst. It's a must have that this needed to be changed to improve the overall gameplay and min/max of formations, hero builds and so on.
2- Making some heroes tankier, or ranged. It might be hard to change how the AI works, but it's much easier to make some heroes tankier or give them ranged weapons. Elena and avalon for example don't have any melee skills and they do no damage at all. While putting all heroes on the backline and protecting them have always been a thing, it's really frustrating when they die for no reason. It's just a bad mechanic. Reverting the nerf of patch 1.14 to Virion passive shield also might be a good idea since for 3 of the 4 races his only use at the moment is as a "tank".
3- Giving the ranged units on wall a real pattern on how they work. Not only it's frustrating to do siege and having a random chance of your catapults being sniped, but it's also not good to have random actions of the AI. The game should make them attack the catapults first or make them attack the frontline first, having both the options only makes formations on siege less fun to use unless you find the right pattern. It take time, and you can never change it when you get bored or want to try new things. Not only it's different for each lvl of units but it's also different for units on wall and on ground, it's really random. The closes answer to solve the problem we have so far is leaving no gaps and using a VERY limited number of formations that keep working even when your troops lvl up. Not fun.
4- Only house members being able to see cross defenses on cities. There's no good reason for the whole kingdom being able to see cross defenses, it just open space for spy and now that zones are lower lvl than before, it's even easier to put a castle to lvl 10-12 and be able to see pretty much the whole area your kingdom posses, unless you dominated the whole map.
5- No more dead bodies of giant troops. Yes, it should be a fun mechanic but it's buggy and doesn't work as intended. At the moment it works as a glue-wall and not like Avril ice wall for example, it's open for the devs to choose if they want to fix it or just remove the dead bodies, I prefer the second option.
6- A in-game clock with server time.
Now one that I didn't want to put on numbers and is open to discussion is lowering the heal time for troops, not only troops on walls. At the moment the defense side have a big advantage and while the heal time is better than it was on the past (very few better), it's still too long. It just makes people wanting to use only bronzes, not only for the cost of a full deploy of silvers/golds but also for the days or even weeks of heal time and we keep things on a forever stalemate.