MOAR CARDS!!!
I also like the forging ideas in the links. It would make relics valuable if you needed to save them for forging, and it would be both a way to assemble existing rares more easily for new players, as well as a way to get access to rares only obtainable by forging. Maybe even a (very very hard) way to forge nymphs or marks?
Also, MOAR CARDS!!!
A supported tournament interface and a way for organizers to spectate fully, beyond what people can ordinarly do, as well as blocking nonorganizers from spectating tournament matches. (to prevent people seeing others strategy beforehand) The current system causes issues when disputes arise. For instance, I once was beating an opponent in a tournament, and he claimed in chat that I had disconnected as he was beating me down with six jade dragons and wanted to be given the win. I screenshotted the field where I had a shield, pulverizer, and about 20 creatures/permanents, and he had no permanents, creatures, or towers except Hope and I think one other card, and me at full life and him almost dead. The organizer looked to me like they were going to call it a draw even after I linked the screenshot in chat, but the other player realized he'd been caught in the act and withdrew. I saw another case where due to a bug, both players claimed that they had won the game. (something weird with antimattered vampires or some other unusual death, based on the timing that things were processed, and apparently was displayed differently on each side) I've also seen where one player gets disconnected and the other player doesn't know it, and keeps playing against an AI. It would make things a lot nicer in tournaments, and less issues for both players and organizers.
We need MOAR CARDS, too.
Did I mention we need MOAR CARDS?