Oof on the timing of that General, but still a great pack.
It's tough to come up with mechanics from other card games that would work in Splinterlands, mostly due to the lack of interactivity after the deck-building stage. Maybe some kind of ban list, where before either player starts choosing their team, they have a chance to ban their opponent from playing certain cards. It could even come with a cost, like reducing the mana cap by some percentage, or adding an additional penalty to that player's team.
Hmmm... actually you could do a lot with that outside of banning cards. There could be modes where you each get the chance to add modifiers before the battle starts. There's an opportunity to really expand on the pre-game without changing any of the core battle mechanics. I guess some of the stuff in the land expansion might be similar. We'll have to wait and see on that.
It is what it is :-P I actually just thought of a great use for it as I'm sitting here typing this.
They actually added this in brawls 2.0 - there is now a Guild ability that allows players to ban 1 card from each opponent, in home games.
I really like the sound of this! I really like the idea of running custom battles (like you described or even setting the mana/rules) as well. At least for friendly challenge matches, if not for tournaments. If I want to run an whole tournament that is no magic, no legends - why shouldn't I be able to?
As to the difficulty due to lack of interaction, I can definitely see that - I guess they have already covered a LOT of the basics. I can think of a handful of abilities :-)