I've read about the amount of power the top 20 witnesses have and how they vote for each other, it doesn't seem very likely that this could ever happen in practice, as things stand currently.

Don’t believe the FUD. It is definitely possible for hard working witnesses to work their way to the top by adding value. I’m actually one example ;) as is @followbtcnews and @jesta.

Given that scenario it's hard to see how smaller stakeholders could really get themselves heard.

If you read the whitepaper, that is somewhat by design. It is not necessarily that they have no say, but the voice of the larger stakeholders is intended to have more weight.