Great comment, I tend to agree with your take on the responsibility of the whales as well as the up vote bots.
Personally, I love minnowbooster and think they fill a completly legitimate role on the platform.
If you're a whale there's certainly a lot of pressure from the community to behave in a certain way and I think as long as they have a viable means to earn a good ROI on their investment through community approved use then they'll likely follow one of those paths, ie. delegation/loans/curation etc.. rather than just blatantly upvoting worthless content for the rewards.
I also agree on the spam. You've got to just flag it when you see it. Right now though, I think it doesn't happen enough because there's a lot of fear of what kind of backlash you'll incur. Everyone is worried about their reputation taking a hit if you accidentally piss off the wrong user. I think as the user base grows and matures and we get more high level reputation users, we'll see more flagging. This will make it much harder for spammers to get any kind of foothold.
I do led out my SP through @minnowbooster too when I have no time to curate myself. We do have similar vision of Steem/it’s future:).