Of course, Secret Lairs have had bonus cards for a while, but at first these were a fixed card everyone who bought the same lair was guaranteed to get, and not typically something super rare either
You dont need to bounce the land, so its actually pretty reasonable as a way to punish people who dont want to play into your Torrential Gearhulk mana
Lore-wise, there is almost an internal power struggle to determine which one is more important, but when it comes to the cards, you're going to be balancing a life gain and sacrifice strategy
Wrenn: I'm looking for a tree
You could also get some swirly effects to signify mana as well as doodads that look like Phyrexian and planeswalker symbols
Its not hard to make permanents leave the battlefield regularly, especially when the other permanent in the command zone can bring a lot of them back