I've been really enjoying the journey mode so far! The proposed changes seem like good ideas, and I'll be curious to see how they play out in practice. This is JUST my opinion, but in the proposed system I think it would be worth limiting the number of cards you can discard/draw each round to prevent simply spamming the discard option until you get your ideal hand. That might have already been implied, but maybe 1 additional discard/draw per round, or 2x/fight or something along those lines.
Finally, as another small note, I think it would be helpful to have just one or two more ways to regain a little health mid-battle. The out-of-battle health regen options are great (and maybe even a little too generous on some maps), but adding "regain 2 health" to Episkey, Protego, or similar cards (rather than exclusively affecting shield and status conditions) would be nice, and make everything just a little more dynamic, while not really being all that overpowered. Additionally, in the case of Episkey, that change would be thematically appropriate, because magic CAN heal people who are injured. Just a thought!
Anyway, keep up the great work!