I personally really like being able to choose what I want to upgrade on my character, and the strategy that comes with it. Being able to choose to spend juice on, say, Damage instead of Max Health is something I think is valuable to the game, as it lets the player adjust how hard they want their fights to be and how quickly they want them to be over - like a player-chosen difficulty system. With a "stats level up as you use them" system, I'm not sure this depth would be kept.
I think one of the most satisfying elements of the game as-is is going to a fountain to spend all juice on upgrades, and immediately noticing the difference the upgrades make. With a "stats level up as you use them" replacement, I feel like that sense of a "boost" would be lost.
I think adding more endless content plays more to the game's weaknesses than to its strengths. I like the unique characters to meet and weapons to try, and finding and exploring new authored areas (like the big statues, beneath the trap door, or inside the toilet) is great. Getting a handle of the controls is another big fun factor. Flying around in the far reaches of the map defeating the same enemies over and over is repetitive and gets dull rather quickly, and so is re-fighting bosses for juice. I was compelled to grind to the level cap in both of my playthroughs of this game (once on the current version, once a few versions ago), and the process of doing so is inevitably the least fun part of it. When I finally reached the level cap, I felt relieved I'd officially "finished it" and done everything there was to do, and could stop playing. With the level cap reached, the grinding was officially over, and I was free to move on to other things.
It is currently too easy to max out your character and there is no incentive to continue playing after you've beaten the current bosses. I will solve this by creating infinite scaling for the player and monsters/bosses, and stuff like farmable crafting recipes from bosses/dungeons.
There's not an incentive to keep playing most games after having fought all their bosses. It's not a crime for a game to end when it has nothing left for the player to do. I think focusing on having more of the authored content in the game (i.e. more bosses and areas) would be more rewarding than tweaks that let the player stay in the least fun part of the game forever. (Though this is a pretty biased way of putting it.)
I hope this doesn't come across as mean or contrarian. I'm just concerned because Juice Galaxy has some interesting ideas that I really like, and the concerns in this discussion seem to value very different aspects of the game than what I enjoyed.
Thank you for making Juice Galaxy!