Flamewar, Brash Veteran Flamewar is an interesting commander because when I saw him, the first thing I thought about was Prosper, Tome-Bound
Shalai is mostly bad because it matches poorly against Tempet Djinn, but Sleep is a card actually seeing constructed play now
So, if your key cards are all expensive, you likely need to include some cheaper cards that help build to those other cards and vice versa
Ive been consistently surprised by Stonecoil Serpent in the Arena Cubes, and its a card that falls within the realm of playable even in Vintage Cube, though merely being an artifact is doing a lot of the heavy lifting there
In some games, early turns of land destruction could build up ones advantage so massively that victory became inevitable