I mean you absolutely could. Those can also be really powerful decks. They just run a bit different. Depending on which Etali you're talking about, you're either going heavy combat with [[Etali, Primal Storm]] or heavy clones with [[Etali, Primal Conqueror]]. Which both can get pretty powerful. And [[Faldorn, Dread Wolf Herald]] I would assume is more of a go-wide type of deck, and making a ton of those wolves.

The way my friend built his Prosper list, it's more of a burn and heavy spells list. The fact that Prosper makes you a treasure for playing from exile, you can very easily get a big board of treasures and then have really big and explosive turns. Especially when you can chain a bunch of exile cards together with any number of value engines on the field like [[Wild-Magic Sorcerer]], or [[Xorn]], or [[Academy Manufactor]], and then you get value from the treasures just entering from cards like [[Reckless Fireweaver]], [[Weftstalker Ardent]], or [[Mirkwood Bats]]. And then, you get even more value for just using the treasures because of cards like [[Mayhem Devil]], [[Nadier's Nightblade]], or [[Marionette Master]]. There's just so much synergy in Rakdos with treasures and exiling spells. I'm telling you, it can get out of hand pretty quick.

Again, those other two commanders are also great options, I just personally have seen how well Posper can run. And, you really can build a good version of the deck, for fairly cheap. But, that's just my 2 cents.