Hi Trapez,
Thank you for your extensive proposals. I agree that some effects are not clearly explained with upgrade being the most misunderstood effect in the game.
You are actually allowed to have 6 cards in hand!
By reducing the coin size, what exactly do you mean?
Merging sell / on play effects into one text or numeric icons is definitely something I was looking into but polishing the whole "random card generator" feature was something complex and very time consuming. Definitely the most important part of the game and number 1 priority to improve.
However the game actually have many flaws in game design which could be exploited.
Cheers!