I too would like it better if people could change votes, as often as they like, before the election ends. Against that, CIVS has battle-tested software to get everything else right.
So, if we use CIVS, that’s a tradeoff: people need to be aware that they cannot change their vote. And so they’d be well advised to delay voting until near the end of the voting window.
A good point: CIVS does not close the election on its own. Our election supervisor has to close it “by hand”. So if a slew of last-second voters speaks up saying they need a few more hours, they can get it.
Before then, I expect starting a Discourse approval poll on the PEPs would go a very long way toward spurring the kind of pre-vote discussions we all want to see, along with a (self-selected) sample of how people are leaning. You can change your votes in a Discourse poll as often as you like.
Too painful to be serious: instead of a poll just listing 7 PEPs, we could have a poll with the 7*6 = 42 distinct ordered pairs, where each voter picks the (up to) 7C2 = 21 pair rankings they prefer 
.