In my mind, guilds and factions are very similar, the only way guilds would work, is if they took the place of the current \"Factions\" and factions turned into just a mix of races, like in WOW. you have the two factions (Hord and Alliance) It would make the game a lot more complicated and unnecessary.
I feel as though starmade is a \"Minecraft EvE online\" so factions make sence.