I come back to this periodically, and it's really interesting to see the changes you make. Personally, I find the current unlock system pretty frustrating - it's pretty limiting, and forces you into playing particular strategies that you don't otherwise want to, purely so you can unlock other things, rather than feeling like you're progressing. I've also found that you now (moreso than before) need to have some kind of discard mechanic, in case you fill up the board and can't play anything, so can't get new cards. Deadlocks are not fun. :(