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
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
Sure, useful cards from this part of Magics history can and will spike in price, but Ive seen people worried about the supply of cards like Wall of Kelp
Board & Card Games Stack Exchange Why would you want to play with a deck bigger than 60 cards in MTG
You could also get some swirly effects to signify mana as well as doodads that look like Phyrexian and planeswalker symbols
Svyelun of Sea and Sky Ward 1 is more of an annoyance than a real protective ability, but Svyelun of Sea and Sky has built-in resilience, so your opponent cant brush it aside