At best it would be papering over hole left over by system being weak (or even broken) by design.
20? what if platform grows by order of magnitude? ... two orders of magnitude? ... suddenly finding twenty might be too easy ... then what about having enough whales to curate recommended posts?
Do wealth diffusion rates will be fast enough to keep whales from being overwhelmed?
What if platform does something stupid, or get competition and shrinks? Suddenly hard-coded number will be too much ...
... and then you have ancient problem that one person's treasure is other person's garbage ... and i saw no effort to take on that by steemit ...
... but that discussion probably deserves post of its own :)