Not a whole lot for engines, but Empty the Warrens does naturally work with all of the fast mana we previously mentioned, while not using the same resource as Echo of Eons.The last deckbuilding constraint I would like to address is the symmetric nature of Echo of Eons, you can fix this with non-discard based disruption
If any creatures with banding you control are blocking or being blocked by a creature, you divide that creature's combat damage, not its controller, among any of the creatures it's being blocked by or is blocking.) : Counter target activated ability from an artifact source unless that ability's controller pays
Which is a fun mini-game
Even with that said, it is a mechanic that I would love to see come back, but with a little better fine tuning when it comes to what the generals its stapled to are capable of
This contributes for the variance during games to be much greater and for a great diversity of cards to interact, allowing a greater participation of all players and making each game unique