Even if some people do just vote the top 7/10 witnesses, they'll likely be the lower staked ones who aren't really sure what witnesses are about anyway. So it shouldn't have too much impact, particularly as, like you say, it leaves more space for the popular votes by the bulk of users. I like this idea better than all votes being equal, because it leaves scope for election choices by both those who have a lot of stake monetarily (and possibly a good understanding of how things work) and those with stake in the longevity of steemit, but who can't afford to invest lots.
However, things are never that simple and @sirknight makes a good point in that we risk the lower ranked and new witnesses not getting a foot in the door for being unproven. It's a shame we have to worry about human nature and the risks associated with it.
I definitely feel that inactive witnesses should be dropped out completely after a certain period of inactivity. It's frustrating that we're seeing a list that has so many inactives when there are active ones off the bottom who should be visable.
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The lower ranks might have more opportunity if people stack on the top points because then they only need to convince a few highly staked individuals for a chance to get bumped up heavily. If the large staked players were playing well, they might vote all 7 but have 1-2 votes more dynamic in nature.