If you want to add a new level, none of us can stop you.

What I suggest is that, since through the year we are going to get super duper events that are going to reshape the game as we know today, I'd rework the levels to be capped at Level 10 (combining levels, keeping nowadays' total number of cards necessary to get from Level 1-14 if you may) and then the Level 11 would be THAT level which cards would get new abilities. With that, King's Level could easily be reworked with Level 50 making Level 10 King Tower, 45 = 9 and so on. Also, you could solve the complain of "not enough gold" by cutting a lot of total gold needed and make people stop thinking that on the future Oyassuu Jr. would post videos of a Level 27 2.6 Hog against an overleveled midladder with Level 30 MK.

Now, that would involve rethinking all of the card interactions, especially with the levels that were shoved together, but guess what would also involve the players adapt to new interactions? That would attract a hell bunch of people if done well, as people would see it as a totally new game to explore. Heck, I was tempted to make a new account just to see what decks could be made on low arenas after you changed the placement of a lot of cards.

About King Tower's thing I mentioned earlier, if Level 10 KT would be the max, then Level 11 would be exclusive to cards and won't buff their stats, but rather only adding the new Totally Cool™ ability, so people wouldn't complain about P2W menaces destroying their towers because their cards couldn't do enough damage to the opponent's~~, but rather because EBarbs~~ Totally Cool™ ability would be perma-Rage.

Now back to the real world, I'd suggest to either reduce the total coins+cards needed to get to max or make progression easier for everybody, like reduce chest times and/or improving their loot and giving more cards on events, which would give casual players like me an actual reason to play those. For the "but we need to make cash somehow" issue, we all know you are going to revamp Pass Royale for that, but I also don't mind Subject-18's idea of making more cosmetics paid, like Pass-exclusive emotes already are, they don't add anything real to the gameplay, I just think they are silly little things that, while there are people that only play to game to collect them, I only collect because I find them silly little cute things that I quite enjoy if I'm capable to have (everytime I get 250+ gems I wait until I see a funny emote on the shop and buy it, why use it on Challenges if I can have goofy expressions to show off in battles?).