Those are all good ideas, thanks for sharing! High Altitude is a good name too. That could even be another rule set in addition to blood tax. One takes the 1 health per round, while high altitude starts the fatigue on round one so the damage increases every round.
The cards dealing magic damage taking double magic damage would be fun.
I agree the extra rulesets in champ would make it more interesting. It also makes it more important to have a variety of cards when you get the limiting rule sets.